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Wojciech J. Miloch

Professor

Email w.j.miloch[ ]fys.uio.no

Phone +47 22 85 60 14

Room KV324 (Chemistry building)

Username

Visiting address Sem Sælands vei 24 Fysikkbygningen 0371 OSLO

Postal address Postboks 1048 Blindern 0316 Oslo

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Academic Interests

Plasma physics, space physics, numerical methods.

Plasma simulations, particle-in-cell method, plasma-solid interactions, spacecraft charging, complex plasma, waves and instabilities in plasma.

Higher education and employment history

Employment

Professor (2017 - now)

Associate Professor, Department of Physics, University of Oslo (2013 - 2017)

Postdoctoral research fellow, Department of Physics, University of Oslo (2011 - 2013)

Postdoctoral research fellow, Department of Physics and Technology, University of Tromsø (2010-2011)

Research fellow, Institute of Theoretical Astrophysics, University of Oslo (2006-2009)

Education

Ph.D., Astrophysics, University of Oslo (2009)

MSc, Physics, University of Oslo (2006)

Magister of Philology (MA in language and literature), Slavic Studies, University of Gdansk (2005)

Tags: plasma physics, numerical modeling, space physics, waves, Complex systems, numerical methods, Japan, Russia

Holen, Gaute Arnesson; Mishra, Rinku; Miyake, Y. & Miloch, Wojciech Jacek (2026). Ion trapping around small positively charged objects in magnetized plasma. Physics of Plasmas. ISSN 1070-664X. 33(5). doi: 10.1063/5.0309574. Full text in Research Archive Show summary
We present a novel trapping mechanism for ions around small positively charged objects in magnetized plasma. Here, the Larmor radius is larger than the object, but approximately equal to the characteristic radial length of the object's electrostatic structure. The resulting steady state solution from state-of-the-art particle-in-cell simulations shows a bipolar electric field around the object, with a density enhancement in the quasi-neutral region. Test particle simulations explore the mechanism behind the ion trapping by focusing on single-particle-motion, and transforming the particles to gyro-center, Larmor radius space. We also observe a kinetic energy gradient in the quasi-neutral region, where the ions organize themselves with respect to distance from the object according to their velocity, where the gyro-centers of particles are nearly coincident with the object's position. This leads to a shift in the velocity distribution. Analysis of test particles' temporal evolution in the gyro-center, Larmor radius space reveals regions of instability and stability, which correspondwell with the density enhancement and ion depletion. The results are similar for spherical and cylindrical objects, suggesting that the trapping mechanism is fundamental. These findings have implications for understanding plasma interactions with small objects, with potential applications in space physics, fusion devices, and plasma diagnostics.
Holen, Gaute Arnesson; Mishra, Rinku; Miyake, Y. & Miloch, Wojciech Jacek (2026). Numerical method for dynamic dust charge in molecular dynamics simulations of laboratory and lunar dusty plasma environments. Physics of Plasmas. ISSN 1070-664X. 33(8), p. 083703-1–083703-14. doi: 10.1063/5.0320581. Full text in Research Archive
Maguire, S. J.; Wood, A. G.; Themens, D. R.; Henley, E. M.; Milan, Stephen Eric & Soobiah, Y. [Show all 10 contributors for this article] (2026). The Evolution of a Polar Cap Patch Into a Blob in the Nightside Ionosphere: Direct Observations of Multiple Blob Formation Mechanisms Acting Simultaneously on the Same Plasma. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 131(3). doi: 10.1029/2025JA034402. Full text in Research Archive Show summary
A polar cap patch was observed to exit the polar cap to become a blob as it entered the auroral oval on the nightside of the Earth under moderately quiet geomagnetic conditions (Kp = 3−). Auroral particle precipitation led to an increase in the electron density of the blob. Blobs can be formed by multiple formation mechanisms, including transportation effects and auroral precipitation. This blob exhibited characteristics which fit within the definitions of both boundary and auroral blobs. This study therefore presents direct observations of multiple blob formation mechanisms acting simultaneously on the same plasma. These observations were made using the European Incoherent SCATter (EISCAT) radars. The polar cap patch was first observed in the EISCAT Svalbard Radar (ESR) and is later observed as a blob by the EISCAT VHF and UHF radars as the plasma moves antisunward from the polar cap and into the auroral oval. The Super Dual Auroral Radar Network radars showed that the plasma was moving antisunward and data from the Active Magnetosphere and Planetary Electrodynamics Response Experiment provided supporting evidence for the location of the auroral boundary. In addition, Global Navigation Satellite Systems (GNSS) receivers monitored the scintillation effects that were associated with large-scale structures. Overall, very low scintillation was observed by these receivers, suggesting that small-scale structures (<365 m for GNSS L1 frequencies) did not develop significantly during this period.
Jin, Yaqi; Kotova, Daria; Clausen, Lasse & Miloch, Wojciech Jacek (2025). Significant Plasma Density Depletion From High- to Mid-Latitude Ionosphere During the Super Storm in May 2024. Geophysical Research Letters. ISSN 0094-8276. 52(5). doi: 10.1029/2024GL113997. Full text in Research Archive Show summary
We demonstrate the global response of the ionosphere to the geomagnetic super storm on 10–11 May 2024. The in situ observations from the Swarm spacecraft show a rapid depletion of plasma density in the dawn and dusk sectors following the storm. The in situ data are further complemented by the ground-based total electron content maps. Both the in situ and the ground-based observations show significant depletion of electron density during the super storm in regions above 50° magnetic latitude. The density depletion originates from a polar hole in the morning high latitude sector. It is suggested that the strong convection speed under substantial solar wind forcing leads to chemical composition changes and rapid recombination in the ionosphere. The region of depleted plasma density is not confined to the polar cap but expands to auroral and mid-latitude regions. The depleted plasma density lasts for about 3 days before it recovers to the pre-storm level
Clausen, Lasse; Bekkeng, Tore André; Els, Sebastian; Khoory, Mohammed S.; Sharaf, Ahmed A. & Adhikari, Sayan [Show all 9 contributors for this article] (2025). The Langmuir Probe Instrument on Board the Rashid-1 Rover of the Emirates Lunar Mission. Space Science Reviews. ISSN 0038-6308. 221, p. 1–17. doi: 10.1007/s11214-025-01159-5. Full text in Research Archive Show summary
The Rashid-1 rover, which was part of the Emirates Lunar Mission (ELM) program, was a small rover aimed to be operated for one lunar day on the lunar surface. As part of its scientific instrumentation, Rashid-1 carried a Langmuir probe experiment (LNG) in order to provide the first extensive, high-resolution in situ measurements of the bulk parameters of the lunar dayside thermal plasma at different altitudes above the lunar surface. The LNG was comprised of four probes, mounted at different locations and heights above the lunar surface on the Rashid-1 rover. This way, the LNG was intended to derive an altitude profile of the two plasma parameters electron density and electron temperature above the lunar surface. The design of the instrument and a description of the data analysis technique, calibration, and validation are provided in this paper. Due to the short separation between the probes and the rover body (in terms of Debye length), the measurements of the LNG were expected to be influenced by the presence of the rover and its sheath. This was addressed through numerical modeling, which is described and preliminary results are presented. Unfortunately, the landing in the Atlas crater of the lunar lander carrying Rashid-1 to the surface was not successful – however, this description of the instrument design and the data analysis techniques are still useful for future explorations of the lunar plasma environment.
Kotova, Daria; Sinevich, A.A.; Chernyshov, A.A.; Chugunin, D.V.; Jin, Yaqi & Miloch, Wojciech Jacek (2025). Strong turbulent flow in the subauroral region in the Antarctic can deteriorate satellite-based navigation signals. Scientific Reports. 15(1), p. 3458–3458. doi: 10.1038/s41598-025-86960-6. Full text in Research Archive
Buschmann, Lisa Marie; Asamura, K.; Clausen, Lasse; Jin, Yaqi; Kojima, H. & Kumamoto, A. [Show all 13 contributors for this article] (2025). Plasma structuring within an expanded polar cap and cusp studied with the SS-520-3 sounding rocket. Earth, Planets and Space. ISSN 1343-8832. 77(1). doi: 10.1186/s40623-025-02189-7. Full text in Research Archive Show summary
The SS-520-3 sounding rocket was launched on November 4th, 2021 as part of the Grand Challenge Initiative - Cusp from Ny-Ålesund, Svalbard. The rocket was launched into the cusp ionosphere during the main phase of a geomagnetic storm. In this study we utilize two low energy particle analyzers as well as a multi-needle Langmuir probe and an impedance probe as part of the rocket payload. This study aims to provide an overview of the flight conditions from a range of ground-based instruments and scintillation receivers. We were able to confirm that the rocket entered the cusp through the poleward edge at around 74 ∘ of northern geographic latitude. Additionally, the rocket encountered polar cap patches (PCP), as well as a patch within the cusp (CP) and a newly-formed tongue of ionisation (TOI). Analysis of the density variations within different scale sizes show enhancements within meter-size and kilometer-size scales on the edges of PCP, within the CP and TOI. Overall, the enhancements within the variations on all sizes, as well as enhancements of the electron density were significantly higher within the CP and TOI in comparison to the PCP, though all structures were encountered at similar altitudes. The strongest enhancements were found on the poleward edge of the TOI, corresponding to strong fluctuations within the electron density. The TOI also had the largest enhancements within gradients of kilometer-size in comparison to meter-sizes. As the TOI is convecting with respect to the background plasma, the edges are susceptible to instabilities like the Kelvin–Helmholtz instability (KHI) and Gradient-Drift instability (GDI), giving rise to plasma density structures on several scale sizes. Graphical Abstract
Spogli, Luca; Jin, Yaqi; Urbář, Jaroslav; Wood, Alan G.; Donegan-Lawley, Elizabeth E. & Clausen, Lasse [Show all 20 contributors for this article] (2024). Statistical models of the variability of plasma in the topside ionosphere: 2. Performance assessment. Journal of Space Weather and Space Climate. 14. doi: 10.1051/swsc/2024003. Full text in Research Archive Show summary
Statistical models of the variability of plasma in the topside ionosphere based on the Swarm data have been developed in the “Swarm Variability of Ionospheric Plasma” (Swarm-VIP) project within the European Space Agency’s Swarm+4D-Ionosphere framework. The models can predict the electron density, its gradients for three horizontal spatial scales – 20, 50 and 100 km – along the North-South direction and the level of the density fluctuations. Despite being developed by leveraging on Swarm data, the models provide predictions that are independent of these data, having a global coverage, fed by various parameters and proxies of the helio-geophysical conditions. Those features make the Swarm-VIP models useful for various purposes, which include the possible support for already available ionospheric models and proxy of the effect of ionospheric irregularities of the medium scales that affect the signals emitted by Global Navigation Satellite Systems (GNSS). The formulation, optimisation and validation of the Swarm-VIP models are reported in Paper 1 (Wood et al. 2024. J Space Weather Space Clim. in press). This paper describes the performance assessment of the models, by addressing their capability to reproduce the known climatological variability of the modelled quantities, and the ionospheric weather as depicted by ground-based GNSS, as a proxy for the ionospheric effect on GNSS signals. Additionally, we demonstrate that, under certain conditions, the model can better reproduce the ionospheric variability than a physics-based model, namely the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM).
Pedersen, Christina Alsvik; Njåstad, Birgit; Aas, Wenche; Darelius, Elin Maria K.; Descamps, Sebastien & Flått, Stig [Show all 13 contributors for this article] (2024). The Troll Observing Network (TONe): plugging observation holes in Dronning Maud Land, Antarctica. Polar Research. ISSN 0800-0395. 43. doi: 10.33265/polar.v43.10370. Full text in Research Archive Show summary
Understanding how Antarctica is changing and how these changes influence the rest of the Earth is fundamental to the future robustness of human society. Strengthening our understanding of these changes and their implications requires dedicated, sustained and coordinated observations of key Antarctic indicators. The Troll Observing Network (TONe), now under development, is Norway’s contribution to the global need for sustained, coordinated, complementary and societally relevant observations from Antarctica. When fully implemented within the coming three years, TONe will be a state-of-the-art, multi-platform, multi-disciplinary observing network in data-sparse Dronning Maud Land. A critical part of the network is a data management system that will ensure broad, free access to all TONe data to the international research community.
Mishra, Rinku; Moulick, R.; Adhikari, Sayan; Marholm, Sigvald; Eklund, Anders Johan & Miloch, Wojciech Jacek (2024). Beam–plasma dynamics in finite-length, collisionless inhomogeneous systems. Physics of Plasmas. ISSN 1070-664X. 31(10). doi: 10.1063/5.0218386. Full text in Research Archive Show summary
This study investigates the streaming instability triggered by ion motion in a plasma system that is finite in length, collisionless, and inhomogeneous. Employing numerical simulations using particle-in-cell techniques and kinetic equations, the study examines how inhomogeneity emerges from integrating a cold ion beam with a background plasma within a confined system. The findings suggest that steady ion flow can modify ion sound waves through acoustic reflections from system boundaries, leading to instability. Such phenomena are known to be a hydrodynamic effect. However, there are also signatures of the beam-driven ion sound instability where kinetic resonances play a pivotal role. The main objective is to understand the impact of a finite-length system on beam–plasma instability and to identify the wave modes supported in such configurations.
Sinevich, A.A.; Chernyshov, A.A.; Chugunin, D.V.; Klimenko, M.V.; Panchenko, V.A. & Yakimova, G.A. [Show all 9 contributors for this article] (2024). Multi-Instrument Approach to Study Polarization Jet/SAID and STEVE. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 129(11). doi: 10.1029/2024JA033222. Full text in Research Archive Show summary
In this study, we employ a unique multi-instrumental approach for a comprehensive examination of Polarization Jet (PJ) (or, another name, Subauroral Ion Drift (SAID)). A diverse set of data is used to assess the connection between the appearance of the inhomogeneous structure of PJ/SAID and its reflection in ground-based observations during geomagnetic activity. Our approach combines satellite (Defense Meteorological Satellite Program, NorSat-1, Swarm) and ground-based (ionosondes, magnetometers, GPS/GLONASS receivers) data, allowing us to study PJ/SAID in detail and compare satellite data with ground-based measurements. We describe the characteristic patterns on ionograms that may indicate the presence of PJ/SAID and how ionosondes can be used to study PJ/SAID. Polarization Jet Strata and irregularities of plasma parameters can cause multiple reflections, which are visible in ionograms as F-spread. The splitting of the F2 trace into two or more traces on ionograms may indicate the presence of PJ/SAID near the observation point. Data from GPS/GLONASS receivers in regions where PJ/SAID is observed enable the construction of local total electron content maps, visualizing how PJ/SAID is reflected in those maps. It is shown how the geomagnetic latitude of PJ/SAID changes during the geomagnetic activity. Furthermore, this case is notable because not only PJ/SAID but also STEVE (Strong Thermal Emission Velocity Enhancement) is observed at subauroral latitudes in Northern Europe during the examined geomagnetic event.
Brask, Steffen Mattias; Marholm, Sigvald; Miloch, Wojciech Jacek & Marchand, R. (2024). Effects of guard and boom on needle Langmuir probes studied with particle-in-cell simulations. Journal of Plasma Physics. ISSN 0022-3778. 90(1). doi: 10.1017/S0022377823001411. Full text in Research Archive Show summary
We investigate the effects of different guard geometries on the currents to needle-type Langmuir probes. The results are based on particle-in-cell numerical simulations. We show that if the guard length is less than 6–8 Debye lengths there can be a significant effect on the currents to the probe. A guard radius should not be larger than the Debye length, otherwise it can also significantly affect the currents. However, since guard radii are often close to the probe radius, the second condition is usually satisfied.
Jao, Chun-Sung; Miloch, Wojciech Jacek & Miyake, Yohei (2024). Collected Current by a Double Langmuir Probe Setup With Plasma Flow. IEEE Transactions on Plasma Science. ISSN 0093-3813. 52(10), p. 5222–5233. doi: 10.1109/TPS.2024.3501310. Full text in Research Archive Show summary
The multineedle Langmuir probe (m-NLP) instrument, consisting of two or more fixed-bias cylindrical Langmuir probes, is designed to enhance data resolution, particularly for in situ measurement in space missions. However, like other spacecraft and instruments used in space missions, these probes may interact with the surrounding plasma, potentially leading to errors in plasma measurements. In this article, we investigate the interaction between a double Langmuir probe setup and plasma flow, specifically focusing on how the collected current on the probes is affected by the electric bias and varying distances between the probes. Results from Particle-in-Cell (PIC) simulations show that with a front probe and a rear probe aligned along the plasma flow, not only may the rear probe’s collected current be affected, but the entire system may also experience significant influences if the distance between probes is short. In particular, if both probes are positively biased, as in the m-NLP instrument, they will not significantly influence each other’s measurements if the distance between them is longer than 30 Debye lengths. We also employ test particle simulations to further illustrate the interaction between the double Langmuir probe system and its surrounding plasma.
Holen, Gaute Arnesson; Adhikari, Sayan; Mishra, Rinku & Miloch, Wojciech Jacek (2024). Self-organising phenomena in 2D complex plasma simulations withnon-mono dispersed dust size distributions. Physica Scripta. ISSN 0031-8949. 99(5). doi: 10.1088/1402-4896/ad37dd. Full text in Research Archive Show summary
Complex plasma with a variety of continuous and discrete dust grain size distributions are simulated in 2D with molecular dynamics simulations with radial geometry to determine differences in self-organizing phenomena to more realistically represent the actual in situ variations in dust-size. The standard deviation of particle size σ(a) strongly correlates with phase separation and coupling parameter Γ for all distribution types. We observe local differences in bond order parameters and Voronoi diagrams for different size distributions, and our results suggest that phase transition is affected by continuous size distributions, particularly in the binary distribution case. Simulations with discrete size result in artifacts and discontinuities that are not found in the continuous distributions. The use of continuous distributions is observed to be beneficial both for more realistic approximation of complex plasma experiments and to study systems of strongly coupled particles in general.
Sinevich, A.A.; Chernyshov, A.A.; Chugunin, D.V.; Miloch, Wojciech Jacek & Mogilevsky, M.M. (2024). The Polarization Jet/SAID and Plasma Irregularities of Different Scales. Bulletin of the Russian Academy of Sciences: Physics. ISSN 1062-8738. doi: 10.1134/S1062873823705548. Full text in Research Archive
Brask, Steffen Mattias; Mishra, Rinku; Holen, Gaute Arnesson; Miyake, Y.; Usui, H. & Miloch, Wojciech Jacek (2024). Spherical Langmuir probes in magnetized plasma. A model based on particle-in-cell simulations. Physics of Plasmas. ISSN 1070-664X. 31(2). doi: 10.1063/5.0177775. Full text in Research Archive Show summary
We present a new model for current collected by a spherical Langmuir probe in magnetized plasmas. Data are obtained using state-of-the-art fully 3D kinetic particle-in-cell simulations. We perform a dimensional analysis and use it to determine the appropriate model function. The model is then empirically derived based on the simulation data for a range of probe potentials and magnetic field values with respect to the Debye length. The final model function is applicable to most space plasmas and can easily be generalized.
Wood, Alan G.; Donegan-Lawley, Elizabeth E.; Clausen, Lasse; Spogli, Luca; Urbář, Jaroslav & Jin, Yaqi [Show all 20 contributors for this article] (2024). Statistical models of the variability of plasma in the topside ionosphere: 1. Development and optimisation. Journal of Space Weather and Space Climate. 14. doi: 10.1051/swsc/2024002. Full text in Research Archive Show summary
This work presents statistical models of the variability of plasma in the topside ionosphere based on observations made by the European Space Agency’s (ESA) Swarm satellites. The models were developed in the “Swarm Variability of Ionospheric Plasma” (Swarm-VIP) project within the European Space Agency’s Swarm+4D-Ionosphere framework. The configuration of the Swarm satellites, their near-polar orbits and the data products developed, enable studies of the spatial variability of the ionosphere at multiple scale sizes. The statistical modelling technique of Generalised Linear Modelling (GLM) was used to create models of both the electron density and measures of the variability of the plasma structures at horizontal spatial scales between 20 km and 100 km. Despite being developed using the Swarm data, the models provide predictions that are independent of these data. Separate models were created for low, middle, auroral and polar latitudes. The models make predictions based on heliogeophysical variables, which act as proxies for the solar and geomagnetic processes. The first and most significant term in the majority of the models was a proxy for solar activity. The most common second term varied with the latitudinal region. This was the Solar Zenith Angle (SZA) in the polar region, a measure of latitude in the auroral region, solar time in the mid-latitude region and a measure of latitude in the equatorial region. Other, less significant terms in the models covered a range of proxies for the solar wind, geomagnetic activity and location. In this paper, the formulation, optimisation and evaluation of these models are discussed. The models show very little bias, with a mean error of zero to two decimal places in 14 out of 20 cases. The models capture some, but not all, of the trends present in the data, with Pearson correlation coefficients of up to 0.75 between the observations and the model predictions. The models also capture some, but not all, of the variability of the ionospheric plasma, as indicated by the precision, which ranged between 0.20 and 0.83. The addition of the thermospheric density as an explanatory variable in the models improved the precision in the polar and auroral regions. It is suggested that, if the thermosphere could be observed at a higher spatial resolution, then even more of the variability of the plasma structures could be captured by statistical models. The formulation and optimisation of the models are presented in this paper. The capability of the model in reproducing the expected climatological features of the topside ionosphere, in supporting GNSS-based ionospheric observations and the performance of the model against the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM), are provided in a companion paper (Spogli L et al. 2024. J Space Weather Space Clim https://doi.org/10.1051/swsc/2024003).
Buschmann, Lisa Marie; Clausen, Lasse; Spicher, Andres; Ivarsen, Magnus Fagernes & Miloch, Wojciech Jacek (2024). Statistical Studies of Plasma Structuring in the Auroral Ionosphere by the Swarm Satellites. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 129(2). doi: 10.1029/2023JA032097. Full text in Research Archive Show summary
This study uses over 2 years of 16 Hz density measurements, 50 Hz magnetic field data and ROTI data from the Swarm mission to perform long term statistics of plasma structuring in the polar ionosphere. The timeframe covers more than 2 years near the 24th solar cycle peak. We additionally use 3 years of data obtained from a timeframe close to solar minimum for discussion. We present power spectral densities (PSD) of electron density irregularities and magnetic field for 1‐min intervals. These PSD have been characterized by the probability of a slope steepening, and by integrating the power deposited within frequency intervals corresponding to kilometer scales. For the electron density, we observe seasonal dependencies for both the integrated power and slope characteristics. While the dual slope probability, especially within the polar cap, varies with solar EUV‐radiation, the integrated power is strongest around the equinoxes. Additionally, while we found similar results for the slope probability for both hemispheres, the integrated power exhibits strong hemispheric asymmetries with stronger enhancements within local summer in the southern hemisphere. The ROTI data shows a similar seasonal variability as the density PSD integrated power, in both seasonal dependency and interhemispheric variability. However, for the ROTI data the strongest fluctuations were found within the nightside auroral oval and the cusp. For the PSD of the magnetic field data, we obtain the strongest enhancements within the cusp for all seasons and all hemispheres. The fluctuations may indicate an increase in Alfvénic energy associated with a downward Poynting flux.
Miloch, Wojciech Jacek; Kotova, Daria & Jin, Yaqi (2024). Ionospheric plasma irregularities over Dronning Maud Land in Antarctica and associated space weather effects. Fundamental Plasma Physics. 12. doi: 10.1016/j.fpp.2024.100076. Full text in Research Archive Show summary
Ionospheric plasma irregularities and associated space weather effects over Dronning Maud Land in Antarctica are studied with a multi-instrument approach. It is demonstrated during a substorm event that auroral particle precipitation associated with the edges of auroral arcs can lead to irregularities in the ionospheric plasma density that can have significant impact on trans-ionospheric radio waves. Both refractive and diffractive effects are observed on signals from the GNSS satellites, where the latter are identified by the ionospheric free linear combination approach and amplitude scintillation. Thus, intense auroral particle precipitation can lead to plasma irregularities at scales from several kilometers down to and below the Fresnel radius, and they can result in space weather effects which can lead to losing the integrity of the GNSS signals.
Moulick, Rakesh; Adhikari, Sayan; Sharma, Gunjan; Saikia, B.K. & Miloch, Wojciech Jacek (2024). Particle-In-Cell simulation of electrostatic waves in the ionosphere. Advances in Space Research. ISSN 0273-1177. 73(9), p. 4393–4413. doi: 10.1016/j.asr.2024.02.009. Full text in Research Archive
Enengl, Florine; Spogli, L.; Kotova, Daria; Jin, Yaqi; Oksavik, Kjellmar & Partamies, Noora [Show all 7 contributors for this article] (2024). Investigation of Ionospheric Small-Scale Plasma Structures Associated With Particle Precipitation. Space Weather. 22(1). doi: 10.1029/2023SW003605. Full text in Research Archive Show summary
We investigate the role of auroral particle precipitation in small-scale (below hundreds of meters) plasma structuring in the auroral ionosphere over the Arctic. In this scope, we analyze together data recorded by an Ionospheric Scintillation Monitor Receiver (ISMR) of Global Navigation Satellite System (GNSS) signals and by an All-Sky Imager located in Longyearbyen, Svalbard (Norway). We leverage on the raw GNSS samples provided at 50 Hz by the ISMR to evaluate amplitude and phase scintillation indices at 1 s time resolution and the Ionosphere-Free Linear Combination at 20 ms time resolution. The simultaneous use of the 1 s GNSS-based scintillation indices allows identifying the scale size of the irregularities involved in plasma structuring in the range of small (up to few hundreds of meters) and medium-scale size ranges (up to few kilometers) for GNSS frequencies and observational geometry. Additionally, they allow identifying the diffractive and refractive nature of fluctuations on the recorded GNSS signals. Six strong auroral events and their effects on plasma structuring are studied. Plasma structuring down to scales of hundreds of meters is seen when strong gradients in auroral emissions at 557.7 nm cross the line of sight between the GNSS satellite and receiver. Local magnetic field measurements confirm small-scale structuring processes coinciding with intensification of ionospheric currents. Since 557.7 nm emissions primarily originate from the ionospheric E-region, plasma instabilities from particle precipitation at E-region altitudes are considered to be responsible for the signatures of small-scale plasma structuring highlighted in the GNSS scintillation data.
Jin, Yaqi; Moen, Jøran Idar; Spicher, Andres; Liu, Jianjun; Clausen, Lasse & Miloch, Wojciech Jacek (2023). Ionospheric Flow Vortex Induced by the Sudden Decrease in the Solar Wind Dynamic Pressure. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 128(11). doi: 10.1029/2023JA031690. Full text in Research Archive Show summary
Abrupt changes in the solar wind dynamic pressure can greatly affect the Earth's magnetosphere-ionosphere system. We present an ionospheric flow vortex in the morning sector during the sudden decrease in the solar wind dynamic pressure. The flow vortex was clearly observed by both the Hankasalmi radar and the azimuthal scan mode of the European Incoherent Scatter (EISCAT) Svalbard Radar (ESR). The flow vortex was first seen in the eastern field of view (FOV) of the Hankasalmi radar, and then propagated poleward and westward into the FOV of the ESR. During the passage of the flow vortex, a gradual decrease of electron density was observed by the field-aligned ESR 42 m antenna. When the equatorward directed ionospheric flow reached the ESR site, weak and visible increases in the electron density and electron temperature were observed. This impact was likely caused by soft electron precipitation associated with the clockwise flow vortex and upward field-aligned current. The azimuthal scan mode of the ESR 32 m radar at low elevation angle (30°) allowed us to measure key ionospheric parameters over a larger area (6° in latitude and 120° in azimuthal angle). The latitudinal scan of the electron temperature was used to proxy the equatorward auroral boundary, which shows that the flow vortex was located in the subauroral region. We further demonstrated that it is possible to study the weak increase of electron density by using GPS total electron content (TEC) data. A minor TEC increase was observed near the center of the flow vortex.
Sinevich, A.A.; Chernyshov, A.A.; Chugunin, D.V.; Mogilevsky, M.M. & Miloch, Wojciech Jacek (2023). The Internal Structure of a Polarization Jet/SAID: A Stratified Polarization Jet/SAID. Geomagnetism and Aeronomy. ISSN 0016-7932. 63(6), p. 747–756. doi: 10.1134/S0016793223600583. Full text in Research Archive
Baddeley, Lisa; Lorentzen, Dag Arne; Haaland, Stein Egil; Heino, Erkka Petteri; Mann, Ingrid Brigitte & Miloch, Wojciech Jacek [Show all 10 contributors for this article] (2023). Space and atmospheric physics on Svalbard: a case for continued incoherent scatter radar measurements under the cusp and in the polar cap boundary region. Progress in Earth and Planetary Science. 10. doi: 10.1186/s40645-023-00585-9. Full text in Research Archive Show summary
Incoherent scatter radars (ISRs) represent the only instrument (both ground and space based) capable of making high temporal and spatial resolution measurements of multiple atmospheric parameters—such as densities, temperatures, particle velocities, mass flux—over an altitude range covering the entire mesosphere/lower thermosphere/ionosphere (MLTI) system on a quasi-continuous basis. The EISCAT Svalbard incoherent scatter radar (ESR), located just outside Longyearbyen (78.15∘ N) on Svalbard, is the only currently operating facility capable of making such measurements inside the polar cusp—an area of significant energy input into the atmosphere and characterized by heating instabilities and turbulence. The ESR was built in the mid-1990s and has provided valuable data for the international experimental and modelling communities. New radar technologies are now available, in the form of phased array systems, which offer new data products and operational flexibility. This paper outlines the achievements and current research focus of the ESR and provides scientific arguments, compiled from inputs across the international scientific community, for a new phased array ISR facility on Svalbard. In addition to the fundamental scientific arguments, the paper discusses additional benefits of continued ISR observations on Svalbard, building on the key findings of the ESR. Svalbard has a large network of complementary instrumentation both focused on the MLTI system (e.g. the Kjell Henriksen auroral Observatory, the Svalbard SuperDARN radar and the Svalrak sounding rocket launch facility) with synergies to other research fields, such as meteorology and oceanography. As a further holistic system science view of the Earth becomes more important, a new ISR on Svalbard will be important also in this respect with its ability to provide datasets with a wide range of scientific applications. Increased activity in space has highlighted problematic issues such as space debris. A changing Arctic has also seen increased human activity via the opening up of new shipping routes, which are reliant on GNSS technology that is effected by severe turbulence in the MLTI system. As such, societal applications of a future ISR are also presented. The accessibility and logistical support for such a facility is also briefly discussed.
Buschmann, Lisa Marie; Bonnell, John W.; Bounds, Scott; Clausen, Lasse; Kletzing, Craig & Marholm, Sigvald [Show all 9 contributors for this article] (2023). The role of particle precipitation on plasma structuring at different altitudes by in-situ measurements. Journal of Space Weather and Space Climate. 13. doi: 10.1051/swsc/2023012. Full text in Research Archive Show summary
The plasma in the cusp ionosphere is subject to particle precipitation, which is important for the development of large-scale irregularities in the plasma density. These irregularities can be broken down into smaller scales which have been linked to strong scintillations in the Global Navigation Satellite System (GNSS) signals. We present power spectra for the plasma density irregularities in the cusp ionosphere for regions with and without auroral particle precipitation based on in-situ measurements from the Twin Rockets to Investigate Cusp Electrodynamics-2 (TRICE-2) mission, consisting of two sounding rockets flying simultaneously at different altitudes. The electron density measurements taken from the multi-needle Langmuir probe system (m-NLP) were analyzed for the whole flight duration for both rockets. Due to their high sampling rates, the probes allow for a study of plasma irregularities down to kinetic scales. A steepening of the slope in the power spectra may indicate two regimes, a frequency interval with a shallow slope, where fluid-like processes are dominating, and an interval with a steeper slope which can be addressed with kinetic theory. The steepening occurs at frequencies between 20 Hz and 100 Hz with a median similar to the oxygen gyrofrequency. Additionally, the occurrence of double slopes increases where precipitation starts and throughout the rest of the flight. In addition, strong electron density fluctuations were found in regions poleward of the cusp, thus in regions immediately after precipitation. Furthermore, by investigating the integrated power of the fluctuations within different frequency ranges, we show that at low frequencies (10–100 Hz), the power is pronounced more evenly while the rocket encounters particle precipitation, while at high frequencies (100–1000 Hz) fluctuations essentially coincide with the passing through a flow channel.
Piterskaya, Anna; Miloch, Wojciech Jacek & Mortensen, Mikael (2023). A global spectral-Galerkin investigation of a Rayleigh-Taylor instability in plasma using an MHD-Boussinesq model. AIP Advances. 13(10). doi: 10.1063/5.0155976. Full text in Research Archive Show summary
This paper presents a new efficient algorithm based on the spectral-Galerkin numerical approximations complemented by a magnetohydrodynamics–Boussinesq model and a new solver for studying the development of a Rayleigh–Taylor (RT) instability. We use the Shenfun computational framework in the Cartesian coordinates, which gives the spectral order and accuracy for the considered model based on the magnetohydrodynamics equations and the Boussinesq conjecture. The numerical simulations were conducted for each two- and three-dimensional case, both with and without an external static magnetic field. The validity of the numerical results was examined by comparing the calculated squared L2-norm of the density parameter with the linear stability analysis. We also examined the effects of a uniform tangential magnetic field on the onset and growth of an RT instability at different magnetic field strengths. The analysis of the effectiveness of the presented method suggests that it can be modified for further research on two-component plasma.
Tsagouri, Ioanna; Themens, David R.; Belehaki, Anna; Shim, Ja-Soon; Hoque, Mainul M. & Nykiel, Grzegorz [Show all 10 contributors for this article] (2023). Ionosphere variability II: Advances in theory and modeling. Advances in Space Research. ISSN 0273-1177. doi: 10.1016/j.asr.2023.07.056. Full text in Research Archive
Tsagouri, Ioanna; Belehaki, Anna; Themens, David R.; Jakowski, Norbert; Fuller-Rowell, Tim & Hoque, Mainul M. [Show all 13 contributors for this article] (2023). Ionosphere variability I: Advances in observational, monitoring and detection capabilities. Advances in Space Research. ISSN 0273-1177. doi: 10.1016/j.asr.2023.07.024. Full text in Research Archive
Sinevich, A.A.; Chernyshov, A.A.; Chugunin, D.V.; Clausen, Lasse; Miloch, Wojciech Jacek & Mogilevsky, M.M. (2023). Stratified Subauroral Ion Drift (SSAID). Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 128(3). doi: 10.1029/2022JA031109. Full text in Research Archive Show summary
Abstract In this paper, the internal structuring of Polarization Jet (PJ)/Subauroral Ion Drift (SAID) is studied. It is shown that PJ/SAID consists of several Polarization Jet Strata (PJS) of electron density and temperature. A new type of phenomena has been discovered called Stratified Subauroral Ion Drift (SSAID), which is a PJ/SAID containing small‐scale PJS. Internal small‐scale structure of SSAIDs is measured during various geomagnetic events using data from NorSat‐1, DMSP F‐17 and F‐18 satellites. High resolution measurements on the Norsat‐1 satellite make it possible to detect and study small‐scale structures inside the PJ/SAID, that is, SSAID. The data from DMSP satellites is used to determine explicitly the presence of PJ/SAID during the considered geomagnetic events. Results show that SSAID consist of 2–4 large PJS and from a few units to several tens of small PJS. Large PJS have a size of 0.2°–0.3° latitude and small PJS have a size of <0.1°. Several suggestions regarding possible physical mechanisms of production of SSAID and PJS are presented.
Kjølerbakken, Kai Morgan; Miloch, Wojciech Jacek & Røed, Ketil (2023). Sheath formation time for spherical Langmuir probes. Journal of Plasma Physics. ISSN 0022-3778. 89(1). doi: 10.1017/S0022377822001027. Full text in Research Archive Show summary
The formation time of the surrounding sheath of Langmuir probes in an ionospheric plasma has been studied to better understand the constraints this puts on the sampling frequency of a probe. A fully kinetic three-dimensional particle-in-cell model is used to simulate the temporal effects in the electron saturation region as the sheath forms. The stability of the probe current and the stability of the ion and electron density in the vicinity of the probe have been used to evaluate when the sheath was formed. Simulated results were compared with theoretical models and are in good agreement with the theoretical results. This shows that theoretical models can be used as guidance to estimate the formation time and to determine the sampling rate for a swept bias Langmuir system. Our results also show that the formation time is less affected by the plasma temperature and bias voltage as we move into the thick sheath regime, and will instead be determined by the plasma density. The presented results also show that applying a step function to the probe could be used to characterise ions species composition, or to estimate the ion density.
Sado, Pascal; Clausen, Lasse; Miloch, Wojciech Jacek & Nickisch, H. (2023). Substorm Onset Prediction Using Machine Learning Classified Auroral Images. Space Weather. 21(2), p. 1–9. doi: 10.1029/2022SW003300. Full text in Research Archive Show summary
Abstract We classify all sky images from four seasons, transform the classification results into time‐series data to include information about the evolution of images and combine these with information on the onset of geomagnetic substorms. We train a lightweight classifier on this data set to predict the onset of substorms within a 15 min interval after being shown information of 30 min of aurora. The best classifier achieves a balanced accuracy of 59% with a recall rate of 39% and false positive rate of 20%. We show that the classifier is limited by the strong imbalance in the data set of approximately 50:1 between negative and positive events. All software and results are open source and freely available.
Ssessanga, Nicholas; Miloch, Wojciech Jacek; Clausen, Lasse & Kotova, Daria (2023). Performance Analysis of a Strong Constraint 4DVar and 4DEnVar on Regional Ionosphere Imaging. Space Weather. 21(12). doi: 10.1029/2023SW003584. Full text in Research Archive Show summary
Abstract Data assimilation (DA) techniques have recently gained traction in the ionospheric community, particularly at regional operational centers where more precise data are becoming prevalent. At center stage is the argument over which technique or scheme merits realization. At 4DSpace, we have in‐house developed and assessed the performance of two regional flavors of short‐term forecast strong constraint four‐dimensional (4D, space and time) variational (SC4DVar) DA schemes; the orthodox incremental (SC4DVar‐Inc) and ensemble‐based (SC4DEnVar) approach. SC4DVar‐Inc is bottled‐necked by expensive Tangent Linear Models (TLMs) and model Ad‐joints (MAs), while SC4DEnVar design mitigates these limitations. Both schemes initialize from the same background (IRI‐2016), and electron densities forward propagated (30‐min) by a Gauss Markov filter‐ the densities take on a log‐normal distribution to assert the mandatory ionosphere density positive definiteness. Preliminary assimilation is performed only with ubiquitous Global Navigation Satellite System observables from ground‐based receivers, with a focus on moderately stable mid‐latitudes, specifically the Japanese archipelago and neighboring areas. Using a simulation analysis, we find that under model space localization, 30 member Ensembles are sufficient for regional SC4DEnVar. Verification of reconstructions is with independent observations from ground‐based ionosonde and satellite radio occultations: the performance of both schemes is fairly adequate during the quiet period when the background has a better estimation of the hmF2. SC4DVar‐Inc is slightly better over areas densely populated with measurements, but SC4DEnVar estimates the overall 3D ionosphere picture better, particularly in remote areas and during severe conditions. These results warrant SC4DEnVar as a better candidate for precise short‐time regional forecasts.
Enengl, Florine; Kotova, Daria; Jin, Yaqi; Clausen, Lasse & Miloch, Wojciech Jacek (2023). Ionospheric plasma structuring in relation to auroral particle precipitation. Journal of Space Weather and Space Climate. 13(4). doi: 10.1051/swsc/2022038. Full text in Research Archive
Sarris, Theodoros; Palmroth, Minna; Aikio, Anita; Buchert, Stephan Christoph; Clemmons, James & Clilverd, Mark [Show all 29 contributors for this article] (2023). Plasma-neutral interactions in the lower thermosphere-ionosphere: The need for in situ measurements to address focused questions. Frontiers in Astronomy and Space Sciences. 9. doi: 10.3389/fspas.2022.1063190. Full text in Research Archive Show summary
The lower thermosphere-ionosphere (LTI) is a key transition region between Earth’s atmosphere and space. Interactions between ions and neutrals maximize within the LTI and in particular at altitudes from 100 to 200 km, which is the least visited region of the near-Earth environment. The lack of in situ co-temporal and co-spatial measurements of all relevant parameters and their elusiveness to most remote-sensing methods means that the complex interactions between its neutral and charged constituents remain poorly characterized to this date. This lack of measurements, together with the ambiguity in the quantification of key processes in the 100–200 km altitude range affect current modeling efforts to expand atmospheric models upward to include the LTI and limit current space weather prediction capabilities. We present focused questions in the LTI that are related to the complex interactions between its neutral and charged constituents. These questions concern core physical processes that govern the energetics, dynamics, and chemistry of the LTI and need to be addressed as fundamental and long-standing questions in this critically unexplored boundary region. We also outline the range of in situ measurements that are needed to unambiguously quantify key LTI processes within this region, and present elements of an in situ concept based on past proposed mission concepts.
Jin, Yaqi; Miloch, Wojciech Jacek; Kotova, Daria; Jacobsen, Knut Stanley; Stevanović, Đorđe & Clausen, Lasse [Show all 8 contributors for this article] (2023). Modeling TEC Irregularities in the Arctic Ionosphere Using Empirical Orthogonal Function Method. Space Weather. 21(8). doi: 10.1029/2023SW003531. Full text in Research Archive Show summary
Abstract We develop a climatological model for the Arctic ionosphere based on more than one solar cycle of data (2010–2021) of the rate of change of the total electron content index (ROTI) maps from the International GNSS Service (IGS). The IGS ROTI maps are daily averaged in magnetic latitude and local time coordinates. To develop a climatological model, the ROTI maps are decomposed into base functions and coefficients using the empirical orthogonal function (EOF) method. The EOF method converges very quickly, and the first four EOFs reflect the majority (96%) of the total data variability. Furthermore, different EOF components can reflect different drivers of ionospheric irregularities. The first EOF reflects the averaged ROTI activity and the impact of the solar radiation and geomagnetic activity; the second EOF reflects the impact of the interplanetary magnetic field (IMF) Bz and electric field; the third and fourth EOFs reflect the dawn‐dusk asymmetry around the auroral oval and polar cap, and they can be related to the IMF By. To build an empirical model, we fit the EOF coefficients using helio‐geophysical indices from four different categories (solar activity; geomagnetic indices; IMF; the solar wind coupling function). The final EOF model is dependent on seven selected indices (F10.7P, Kp, Dst, Bt, By, Bz, and E KL ). The statistical data‐model comparisons show satisfactory results with a good correlation coefficient. However, the model cannot capture the significant expansion of the dayside ROTI activity during strong geomagnetic storms. Future effort is needed to provide corrections to the model during severe storms.
Sarris, Theodore E.; Tourgaidis, Stelios; Pirnaris, Panagiotis; Baloukidis, Dimitris; Papadakis, Konstantinos & Psychalas, Christos [Show all 42 contributors for this article] (2023). Daedalus MASE (mission assessment through simulation exercise): A toolset for analysis of in situ missions and for processing global circulation model outputs in the lower thermosphere-ionosphere. Frontiers in Astronomy and Space Sciences. 9. doi: 10.3389/fspas.2022.1048318. Full text in Research Archive Show summary
Daedalus MASE (Mission Assessment through Simulation Exercise) is an open-source package of scientific analysis tools aimed at research in the Lower Thermosphere-Ionosphere (LTI). It was created with the purpose to assess the performance and demonstrate closure of the mission objectives of Daedalus, a mission concept targeting to perform in-situ measurements in the LTI. However, through its successful usage as a mission-simulator toolset, Daedalus MASE has evolved to encompass numerous capabilities related to LTI science and modeling. Inputs are geophysical observables in the LTI, which can be obtained either through in-situ measurements from spacecraft and rockets, or through Global Circulation Models (GCM). These include ion, neutral and electron densities, ion and neutral composition, ion, electron and neutral temperatures, ion drifts, neutral winds, electric field, and magnetic field. In the examples presented, these geophysical observables are obtained through NCAR’s Thermosphere-Ionosphere-Electrodynamics General Circulation Model. Capabilities of Daedalus MASE include: 1) Calculations of products that are derived from the above geophysical observables, such as Joule heating, energy transfer rates between species, electrical currents, electrical conductivity, ion-neutral collision frequencies between all combinations of species, as well as height-integrations of derived products. 2) Calculation and cross-comparison of collision frequencies and estimates of the effect of using different models of collision frequencies into derived products. 3) Calculation of the uncertainties of derived products based on the uncertainties of the geophysical observables, due to instrument errors or to uncertainties in measurement techniques. 4) Routines for the along-orbit interpolation within gridded datasets of GCMs. 5) Routines for the calculation of the global coverage of an in situ mission in regions of interest and for various conditions of solar and geomagnetic activity. 6) Calculations of the statistical significance of obtaining the primary and derived products throughout an in situ mission’s lifetime. 7) Routines for the visualization of 3D datasets of GCMs and of measurements along orbit. Daedalus MASE code is accompanied by a set of Jupyter Notebooks, incorporating all required theory, references, codes and plotting in a user-friendly environment. Daedalus MASE is developed and maintained at the Department for Electrical and Computer Engineering of the Democritus University of Thrace, with key contributions from several partner institutions.
Spicher, Andres; LaBelle, James; Bonnell, John W.; Roglans, Roger; Moser, Chrystal & Fuselier, Stephen A. [Show all 18 contributors for this article] (2022). Interferometric Study of Ionospheric Plasma Irregularities in Regions of Phase Scintillations and HF Backscatter. Geophysical Research Letters. ISSN 0094-8276. 49(12). doi: 10.1029/2021GL097013. Full text in Research Archive Show summary
We investigate the nature of small-scale irregularities observed in the cusp by the Twin Rockets to Investigate Cusp Electrodynamics-2 (TRICE-2) in regions of enhanced phase scintillations and high-frequency coherent radar backscatter. We take advantage of the fact that the irregularities were detected by spatially separated probes, and present an interferometric analysis of both the observed electron density and electric field fluctuations. We provide evidence that fluctuations spanning a few decameters to about a meter have low phase velocity in the plasma reference frame and are nondispersive, confirming that decameter-scale irregularities follow the E × B velocity. Furthermore, we show that these “spatial” structures are intermittent and prominent outside of regions with strongest precipitation. The observations are then discussed in the context of possible mechanisms for irregularity creation.
Kjølerbakken, Kai Morgan; Miloch, Wojciech Jacek; Martinsen, Ørjan Grøttem; Pabst, Oliver & Røed, Ketil (2022). Numerical Study of Non-Linear Effects for a Swept Bias Langmuir Probe. IEEE Transactions on Plasma Science. ISSN 0093-3813. 50(5), p. 1237–1245. doi: 10.1109/TPS.2022.3164220. Full text in Research Archive Show summary
We present a numerical study disclosing non-linear effects and hysteresis loops for a swept bias Langmuir probe. A full kinetic particle in cell (PIC) model has been used to study the temporal sheath effects and the probe current. Langmuir "close to steady state" condition is required to characterize the plasma. However, during operations above frequencies normally used, capacitive and non-linear resistive effects are being unveiled. We demonstrate how ion and electron density and temperature change properties of the probe-plasma system. We also show that a swept Langmuir probe exhibits essential properties described as the "fingerprint of memristors" and how a Langmuir probe can be identified as a transversal memristor. Understanding non-linear processes might enable new ways to operate Langmuir probes with higher sampling rates and better accuracy.
Jin, Yaqi; Clausen, Lasse; Miloch, Wojciech Jacek; Høeg, Per; Jarmołowski, Wojciech & Wielgosz, Pawel [Show all 13 contributors for this article] (2022). Climatology and modeling of ionospheric irregularities over Greenland based on empirical orthogonal function method. Journal of Space Weather and Space Climate. 12(23). doi: 10.1051/swsc/2022022. Full text in Research Archive Show summary
This paper addresses the long-term climatology (over two solar cycles) of total electron content (TEC) irregularities from a polar cap station (Thule) using the rate of change of the TEC index (ROTI). The climatology reveals variabilities over different time scales, i.e., solar cycle, seasonal, and diurnal variations. These variations in different time scales can be explained by different drivers/contributors. The solar activity (represented by the solar radiation index F10.7P) dominates the longest time scale variations. The seasonal variations are controlled by the interplay of the energy input into the polar cap ionosphere and the solar illumination that damps the amplitude of ionospheric irregularities. The diurnal variations (with respect to local time) are controlled by the relative location of the station with respect to the auroral oval. We further decompose the climatology of ionospheric irregularities using the empirical orthogonal function (EOF) method. The first four EOFs could reflect the majority (99.49%) of the total data variability. A climatological model of ionospheric irregularities is developed by fitting the EOF coefficients using three geophysical proxies (namely, F10.7P, Bt, and Dst). The data-model comparison shows satisfactory results with a high Pearson correlation coefficient and adequate errors. Additionally, we modeled the historical ROTI during the modern grand maximum dating back to 1965 and made the prediction during solar cycle 25. In such a way, we can directly compare the climatic variations of the ROTI activity across six solar cycles.
Paziewski, Jacek; Høeg, Per; Sieradzki, Rafal; Jin, Yaqi; Jarmolowski, Wojciech & Hoque, M. Mainul [Show all 12 contributors for this article] (2022). The implications of ionospheric disturbances for precise GNSS positioning in Greenland. Journal of Space Weather and Space Climate. 12. doi: 10.1051/swsc/2022029. Full text in Research Archive Show summary
Ionospheric irregularities impair Global Navigation Satellite System (GNSS) signals and, in turn, affect the performance of GNSS positioning. Such effects are especially evident at low and high latitudes, which are currently gaining the attention of research and industry sectors. This study evaluates the impact of ionospheric irregularities on GNSS positioning in Greenland. We assess the performance of positioning methods that meet the demands of a wide range of users. In particular, we address the needs of the users of mass-market single-frequency receivers and those who require a solution of high precision provided by geodetic dual-frequency receivers. We take advantage of the datasets collected during three ionospheric storms: the St. Patrick’s Day storm of March 17, 2015, the storm on June 22, 2015, and another on August 25–26, 2018. We discover a significant impact of the ionospheric disturbances on the ambiguity resolution performance and the accuracy of the float solution in Real Time Kinematics (RTK) positioning. Next, assessing the single-frequency ionosphere-free Precise Point Positioning (PPP), we demonstrate that the model is generally unaffected by ionospheric disturbances. Hence, the model is predestined for the application by the users of single-frequency receivers in the areas of frequent ionospheric disturbances. Finally, based on the observation analyses, we reveal that phase signals on the L2 frequency band are more prone to cycle slips induced by ionospheric irregularities than those transmitted on the L1. Such signal properties explain a noticeable decline in the dual-frequency RTK performance during the ionospherically disturbed period and merely no effect for the single-frequency ionosphere-free PPP model.
Alfonsi, Lucilla; Bergeot, Nicolas; Cilliers, Pierre J.; Franceschi, Giorgiana De; Baddeley, Lisa & Correia, Emilia [Show all 38 contributors for this article] (2022). Review of Environmental Monitoring by Means of Radio Waves in the Polar Regions: From Atmosphere to Geospace. Surveys in geophysics. ISSN 0169-3298. 43, p. 1609–1698. doi: 10.1007/s10712-022-09734-z. Full text in Research Archive Show summary
The Antarctic and Arctic regions are Earth's open windows to outer space. They provide unique opportunities for investigating the troposphere–thermosphere–ionosphere–plasmasphere system at high latitudes, which is not as well understood as the mid- and low-latitude regions mainly due to the paucity of experimental observations. In addition, different neutral and ionised atmospheric layers at high latitudes are much more variable compared to lower latitudes, and their variability is due to mechanisms not yet fully understood. Fortunately, in this new millennium the observing infrastructure in Antarctica and the Arctic has been growing, thus providing scientists with new opportunities to advance our knowledge on the polar atmosphere and geospace. This review shows that it is of paramount importance to perform integrated, multi-disciplinary research, making use of long-term multi-instrument observations combined with ad hoc measurement campaigns to improve our capability of investigating atmospheric dynamics in the polar regions from the troposphere up to the plasmasphere, as well as the coupling between atmospheric layers. Starting from the state of the art of understanding the polar atmosphere, our survey outlines the roadmap for enhancing scientific investigation of its physical mechanisms and dynamics through the full exploitation of the available infrastructures for radio-based environmental monitoring.
Kotova, Daria; Jin, Yaqi & Miloch, Wojciech Jacek (2022). Interhemispheric variability of the electron density and derived parameters by the Swarm satellites during different solar activity. Journal of Space Weather and Space Climate. 12, p. 1–21. doi: 10.1051/swsc/2022007. Full text in Research Archive Show summary
With the data from the Swarm satellite mission, we study the variability of ionospheric plasma parameters for low and high solar activities. We focus on the electron density measured by Swarm and derived parameters and analyze the variability of these parameters in the contexts of the Northern and Southern hemispheres, specific latitudinal regions, and the solar activity level. We consider two time intervals: with high solar activity (HSA) from August 2014 to July 2015 and with low solar activity (LSA) from January to December 2018. We show that the electron density is described mainly by three probability density functions (PDF): exponentiated Weibull, lognormal, and chi distributions. These results with PDFs can be applied to the modeling or prediction of ionospheric parameters in different regions. The best fit of PDFs was obtained for low and mid-latitudes, while at high latitudes and in the polar caps, the double-peaked features of the distribution require the fit of multiple PDFs. The electron density (Ne) distribution at low latitudes follows more a lognormal distribution, while in the high latitude region, the chi distribution prevails. Different results were obtained for the rate of change of density index (RODI) with two fitting PDFs: lognormal or exponentiated Weibull, where the best fits are for high latitudes and polar caps. We demonstrate high variability in the electron density and derived parameters at low latitudes and in the polar caps. Comparing both hemispheres, we obtained higher values of these parameters during the solar minimum in the Southern hemisphere at high latitudes and polar caps, while for the Northern hemisphere, higher values were obtained at low latitudes. The dependence on the satellite’s altitude was also considered. The main patterns in the diurnal variation of parameters in different regions do not depend on the level of solar activity (which affects only the maximum values). The largest asymmetry between both hemispheres in Ne diurnal distribution was obtained for the polar cap regions. Here a 50% decrease in Ne was observed in the Northern hemisphere during HSA in the early morning sector (04–07 Magnetic Local Time), which has not yet been observed in the Southern hemisphere. For the first time, such a global statistical characterization of the ionospheric plasma density based on the in situ data is presented.
Kotova, Daria; Jin, Yaqi; Spogli, Luca; Wood, Alan G.; Urbar, Jaroslav & Rawling, James T. [Show all 11 contributors for this article] (2022). Electron density fluctuations from Swarm as a proxy for ground-based scintillation data: A statistical perspective. Advances in Space Research. ISSN 0273-1177. doi: 10.1016/j.asr.2022.11.042. Full text in Research Archive Show summary
The Swarm satellite mission has been used for numerous studies of the ionosphere. Here we use a global product, based on electron density measurements from Swarm that characterises ionospheric variability. The IPIR (Ionospheric Plasma IRregularities product) provides characteristics of plasma irregularities in terms of their amplitudes, gradients and spatial scales and assigns them to geomagnetic regions. Ionospheric irregularities and fluctuations are often the cause of errors in position, navigation, and timing (PNT) based on the Global Navigation Satellite Systems (GNSS), in which signals pass through the ionosphere. The IPIR dataset also provides an indication, in the form of a numerical value index (IPIR index), of the severity of irregularities affecting the integrity of trans-ionospheric radio signals and hence, the accuracy of GNSS positioning. We analysed datasets from Swarm A and ground-based scintillation receivers. Time intervals (when Swarm A passes over the field of view of the ground-based GPS receiver) are compared to ground-based scintillation data, collecting an azimuthal selection of the GNSS data relevant to the Swarm satellite overpass. We provide validations of the IPIR product against the ground-based measurements from 23 ground-based receivers, focusing on GPS TEC and scintillation data in low-latitude, auroral and polar regions, and in different longitudinal sectors. We have determined the median, mean, maximum and standard deviation of the parameter values for both datasets and each conjunction point. We found a weak correlation of the intensity of both phase and amplitude scintillation with the IPIR index.
Urbar, Jaroslav; Spogli, Luca; Cicone, Antonio; Clausen, Lasse; Jin, Yaqi & Wood, Alan G. [Show all 11 contributors for this article] (2022). Multi-scale response of the high-latitude topside ionosphere to geospace forcing. Advances in Space Research. ISSN 0273-1177. doi: 10.1016/j.asr.2022.06.045. Full text in Research Archive Show summary
We investigate the response of the topside ionosphere, auroral and polar sectors, to the forcing of the geospace during September 2017. Specifically, we aim at characterizing such a response in terms of the involved spatial scales and of their intensification during the different auroral and polar cap activity conditions experienced in the selected month, that is characterized by severe geomagnetic storm conditions. For our purposes, we leverage on and compare various in situ plasma density data products provided by the Swarm constellation of the European Space Agency (ESA). The spatio-temporal variability of the involved scales in the plasma density observation is featured through the application of the Fast Iterative Filtering (FIF) signal decomposition technique and, for the first time in the ionospheric field, of a FIF-derived dynamical spectrum called “IMFogram”. The instantaneous time-frequency representation provided through the IMFogram illustrates the time development of the multi-scale processes with spatial and temporal resolutions higher than those obtained with traditional signal processing techniques. To demonstrate this, the IMFogram is tested against Fast Fourier and Continuous Wavelet Transforms. With our fine characterization, we highlight how scale cascading and intensification processes in the plasma density observations follow the ionospheric currents activity, as depicted through the auroral activity and polar cap indices, and through the field-aligned currents data product provided by Swarm.
Belakhovsky, V.B.; Jin, Yaqi & Miloch, Wojciech Jacek (2022). Dayside Scintillations of GPS Signals According to the Observations on the Svalbard Archipelago. Bulletin of the Russian Academy of Sciences: Physics. ISSN 1062-8738. 86(3), p. 348–353. doi: 10.3103/S1062873822030066. Full text in Research Archive
Brask, Steffen Mattias; Marholm, Sigvald; Mare, Francesca Di; Adhikari, Sayan; Spicher, Andres & Takahashi, T. [Show all 7 contributors for this article] (2022). Electron-neutral collisions effects on Langmuir probe in the lower E-region ionosphere. Physics of Plasmas. ISSN 1070-664X. 29(3). doi: 10.1063/5.0079761. Full text in Research Archive Show summary
We present the first set of particle-in-cell simulations including Monte Carlo collisions between charged and neutral particles used to simulate a cylindrical Langmuir probe in the electron saturation regime with a collisional electron sheath. We use a setup focused on the E-region ionosphere; however, the results of these simulations are analyzed in a general sense using dimensionless values. We find that the electron currents get enhanced as the collision frequency for electrons increases and the values of 𝜆��𝑒��/𝜆��𝐷��→1, where λe is the electron mean free path and λD is the electron Debye length. In addition, we apply the simulation results to a sounding rocket experiment and show how we can correct the currents for the Investigation of Cusp Irregularities-4 sounding rocket due to collisions while it flies through the E-region.
Sinevich, A.A.; Chernyshov, A.A.; Chugunin, D.V.; Oinats, A.V.; Clausen, Lasse & Miloch, Wojciech Jacek [Show all 8 contributors for this article] (2022). Small-Scale Irregularities Within Polarization Jet/SAID During Geomagnetic Activity. Geophysical Research Letters. ISSN 0094-8276. 49(8). doi: 10.1029/2021GL097107. Full text in Research Archive Show summary
We study the spatial structure of a polarization jet/Sub-Auroral Ion Drift (PJ/SAID) based on data from the NorSat-1 and Swarm satellites during a geomagnetic storm. Observations of plasma parameters inside the PJ/SAID are obtained with NorSat-1 using a system of Langmuir probes with a nominal sampling rate of up to 1 kHz, which allowed measurements with such a high temporal resolution for the first time. A comparative analysis of plasma parameters and electron density spectra inside PJ according to the data from both satellites is presented. Our results show that fluctuations of plasma parameters inside the PJ increase at all scales with increasing geomagnetic activity. Small-scale irregularities in the PJ are measured in situ down to hundreds of meters. The role of large-scale effects in the PJ increases in comparison with the small-scale ones during high geomagnetic activity. The PJ consists of structures ∼0.2° latitude in size within which small-scale irregularities are present.
Jin, Yaqi; Kotova, Daria; Xiong, Chao; Brask, Steffen Mattias; Clausen, Lasse & Kervalishvili, Guram [Show all 8 contributors for this article] (2022). Ionospheric Plasma IRregularities - IPIR - data product based on data from the Swarm satellites. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 127(4). doi: 10.1029/2021JA030183. Full text in Research Archive
Wood, Alan G.; Alfonsi, Lucilla; Clausen, Lasse; Jin, Yaqi; Spogli, Luca & Urbář, Jaroslav [Show all 19 contributors for this article] (2022). Variability of Ionospheric Plasma: Results from the ESA Swarm Mission. Space Science Reviews. ISSN 0038-6308. 218(6). doi: 10.1007/s11214-022-00916-0. Full text in Research Archive Show summary
Abstract Swarm is the first European Space Agency (ESA) constellation mission for Earth Observation. Three identical Swarm satellites were launched into near-polar orbits on 22 November 2013. Each satellite hosts a range of instruments, including a Langmuir probe, GPS receivers, and magnetometers, from which the ionospheric plasma can be sampled and current systems inferred. In March 2018, the CASSIOPE/e-POP mission was formally integrated into the Swarm mission through ESA’s Earthnet Third Party Mission Programme. Collectively the instruments on the Swarm satellites enable detailed studies of ionospheric plasma, together with the variability of this plasma in space and in time. This allows the driving processes to be determined and understood. The purpose of this paper is to review ionospheric results from the first seven years of the Swarm mission and to discuss scientific challenges for future work in this field.
Monte-Moreno, Enric; Hernández-Pajares, Manuel; Yang, Heng; Garcia, Rigo Alberto; Jin, Yaqi & Høeg, Per [Show all 13 contributors for this article] (2021). Method for Forecasting Ionospheric Electron Content Fluctuations Based on the Optical Flow Algorithm. IEEE Transactions on Geoscience and Remote Sensing. ISSN 0196-2892. doi: 10.1109/TGRS.2021.3126888. Full text in Research Archive
Ivarsen, Magnus Fagernes; St-Maurice, Jean-Pierre; Jin, Yaqi; Park, Jaeheung; Miloch, Wojciech Jacek & Spicher, Andres [Show all 8 contributors for this article] (2021). Steepening Plasma Density Spectra in the Ionosphere: The Crucial Role Played by a Strong E-Region. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 126(8). doi: 10.1029/2021JA029401. Full text in Research Archive Show summary
Based on the Swarm 16 Hz Advanced Plasma Density data set, and using the Swarm A satellite, we apply automatic detection of spectral breaks in seven million sampled plasma density power spectra in the high-latitude F-region ionosphere. This way, we survey the presence of plasma irregularity dissipation due to an enhanced E-region conductance, caused both by solar photoionization and particle precipitation. We introduce a new quantity named the steepening slope index (SSI) which we use to estimate the occurrence rate of break-points in sampled plasma densities. We provide an interpretation of SSI in the context of solar photoionization-induced conductance enhancements of the E-region. We present a comprehensive climatology of the SSI occurrence rate, along with statistics documenting characteristic high-latitude plasma density spectra. In the absence of steepening, the typical spectral index is 2.1. When density spectra steepen, the index is typically 1.6 at large scales, and 2.7 at small scales. We discuss the impact of high-energy deeply penetrating electron precipitation in the diffuse aurora, and precipitating electrons in the aurora at large. Here, a key finding is that near the cusp, where the F-region conductance is enhanced, spectra tend not to steepen. We find that both the diffuse and discrete aurora are modulating F-region plasma irregularity dissipation through an enhancement of E-region conductance, highlighting the role played by factors other than solar zenith angle in high-latitude plasma dynamics. The influence of E-region conductance on spectral shapes indicates the need for a new discussion of how particle precipitation can structure the local winter high-latitude F-region ionosphere.
Sado, Pascal; Clausen, Lasse; Miloch, Wojciech Jacek & Nickisch, Hannes (2021). Transfer Learning Aurora Image Classification and Magnetic Disturbance Evaluation. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. doi: 10.1029/2021JA029683. Full text in Research Archive Show summary
We develop an open source algorithm to apply Transfer learning to Aurora image classification and Magnetic disturbance Evaluation (TAME). For this purpose, we evaluate the performance of 80 pretrained neural networks using the Oslo Auroral THEMIS (OATH) data set of all-sky images, both in terms of runtime and their features' predictive capability. From the features extracted by the best network, we retrain the last neural network layer using the Support Vector Machine (SVM) algorithm to distinguish between the labels “arc,” “diffuse,” “discrete,” “cloud,” “moon” and “clear sky/ no aurora”. This transfer learning approach yields 73% accuracy in the six classes; if we aggregate the 3 auroral and 3 non-aurora classes, we achieve up to 91% accuracy. We apply our classifier to a new dataset of 550,000 images and evaluate the classifier based on these previously unseen images. To show the potential usefulness of our feature extractor and classifier, we investigate two test cases: First, we compare our predictions for the “cloudy” images to meteorological data and second we train a linear ridge model to predict perturbations in Earth's locally measured magnetic field. We demonstrate that the classifier can be used as a filter to remove cloudy images from datasets and that the extracted features allow to predict magnetometer measurements. All procedures and algorithms used in this study are publicly available, and the code and classifier are provided, which opens possibility for large scale studies of all-sky images.
Kjølerbakken, Kai Morgan; Miloch, Wojciech Jacek & Røed, Ketil (2021). The influence of probe spacing and probe bias in a double Langmuir probe setup. AIP Advances. 11. doi: 10.1063/5.0058540. Full text in Research Archive Show summary
Multi-needle Langmuir probes are mounted on satellites and sounding rockets for high-frequency characterization of plasma in the ionosphere. Mounted on a spacecraft, the recorded probe current often differs from expected results. In this paper, we perform a numerical study using a particle in cell model to see how the spacing between the individual probes used in a multi-needle setup influences the measured current. We also study how the applied probe bias voltage can contribute to deviations. In our study, we use realistic electron temperatures and electron densities for the relevant part of the ionosphere. However, the results should be generally applicable and valid for other space environments as well as for laboratory Langmuir probe applications. From our study, we can see that when the distance is short, less than two Debye lengths, the current is highly affected, and we can see deviations of more than 60% compared to a single probe setup.
Skjæveland, Arnlaug; Kotova, Daria S. & Miloch, Wojciech J. (2021). Case Studies of Ionospheric Plasma Irregularities Over Queen Maud Land, Antarctica. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 126(10). doi: 10.1029/2021JA029963. Full text in Research Archive Show summary
We use the first data set from the ground-based TEC and scintillation receiver located at the Norwegian Research Station Troll in Queen Maud Land, Antarctica to analyze in detail the ionospheric response during geomagnetic disturbances on February 26-27 and March 18-19, 2018. By combining the Troll data with complementary measurements (scintillation receivers, magnetometers, SuperDARN, DMSP satellites), we demonstrate that plasma irregularities above this part of Queen Maud Land can be associated with the expansion of the auroral oval, related structuring on its edges, as well as with strong flow shears in the evening and at nighttime, which are further modulated by the energetic particle precipitation. Phase scintillation indices correlate well with the magnetometer data.
Mare, Francesca Di; Spicher, Andres; Clausen, Lasse; Miloch, Wojciech Jacek & Moen, Jøran Idar (2021). Turbulence and Intermittency in the Winter Cusp Ionosphere Studied With the ICI Sounding Rockets. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 126(8). doi: 10.1029/2021JA029150. Full text in Research Archive Show summary
The characteristics of turbulent plasma in the winter cusp ionosphere is studied based on in-situ data from the Investigation of Cusp Irregularities (ICI) sounding rockets. The electron density fluctuations from ICI-2 and ICI-3 missions have been analyzed for the whole flight, using advanced timeseries analysis techniques. The analysis of the autocorrelation scale is indicative of the turbulence integral scale and marks the onset of the turbulent cascade from large to small scales in the power spectrum density of the rocket data. The power spectrum is typical for a turbulent field. The turbulent structures are persistent in the data, which are quantified by analyzing the Probability Distribution Functions (PDFs) and their deviations from the Gaussian distribution. The kurtosis analysis indicates the presence of intermittency. These results are compared with the Local Intermittence Measure - LIM, which confirms the presence of small scale intermittent structures. The turbulence measured by rockets appears well developed and covers frequencies between 1 Hz and several hundred Hz. There is a good agreement with the previous results, suggesting that density fluctuations in the ionospheric cusp agree with the turbulence framework in which intermittent processes transfer energy across different scales.
Ivarsen, Magnus Fagernes; Jin, Yaqi; Spicher, Andres; Miloch, Wojciech Jacek & Clausen, Lasse (2021). The Lifetimes of Plasma Structures at High Latitudes. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 126. doi: 10.1029/2020JA028117. Full text in Research Archive Show summary
We present an investigation of polar cap plasma structure lifetimes. We analyze both simulated data from ionospheric models (International Reference Ionosphere model and Mass Spectrometer Incoherent Scatter model) and in situ data from the Swarm satellite mission (the 16 Hz Advanced Plasma Density dataset). We find that the theoretical prediction that E-region conductance is a predictor of F-region polar cap plasma structure lifetimes is indeed supported by both in situ-based observations and by ionospheric models. In situ plasma structure lifetimes correlate well with the ratio of F- to E-region conductance. We present explicit predictions of small scale (∼1 km) structure lifetimes, which range from less than 1 h during local summer to around 3 h during local winter. We highlight a large discrepancy between the observational and theoretical scale-dependency of decay due to diffusion.
Jin, Yaqi; Clausen, Lasse; Spicher, Andres; Ivarsen, Magnus Fagernes; Zhang, Yongliang & Miloch, Wojciech Jacek [Show all 7 contributors for this article] (2021). Statistical Distribution of Decameter Scale (50 m) Ionospheric Irregularities at High Latitudes. Geophysical Research Letters. ISSN 0094-8276. 48(19). doi: 10.1029/2021GL094794. Full text in Research Archive Show summary
We present a study of decameter scale ionospheric irregularities using in-situ electron density data from the NorSat-1 satellite. During the current period of low solar activity, NorSat-1 frequently observes significant plasma irregularities from several 10 s km down to several decameter. These are often observed near the dayside cusp and dawnside auroral zone. The decameter-scale irregularities are positively correlated with intermediate-scale (10 km) density gradients, for both negative and positive gradients encountered by the satellite. The statistical distribution of electron density over two winter months in the northern hemisphere along NorSat-1 orbits, shows significant density increases in the cusp ionosphere (75°–80° Magnetic LATitude) and in regions near the dawnside auroral oval. Intermediate scale density gradients and small-scale irregularities are clearly associated with these density enhancements. We postulate that these density enhancements and irregularities are due to auroral particle precipitation/plasma dynamics.
Belakhovsky, Vladimir Borisovich; Jin, Yaqi & Miloch, Wojciech Jacek (2021). Influence of different types of ionospheric disturbances on GPS signals at polar latitudes. Annales Geophysicae. ISSN 0992-7689. 39, p. 687–700. doi: 10.5194/angeo-39-687-2021. Full text in Research Archive Show summary
Abstract. The comparative research of the influence of different types of auroral particle precipitation and polar cap patches (PCPs) on the global positioning system (GPS) signals disturbances in the polar ionosphere was done. For this purpose, we use the GPS scintillation receivers at Ny-Ålesund and Skibotn, operated by the University of Oslo. The presence of the auroral particle precipitation and polar cap patches was determined by using data from the EISCAT 42m radar on Svalbard. The optical aurora observations in 557.7 and 630.0 nm spectrum lines on Svalbard were used as well for the detection of ionospheric disturbances. The cusp identification was done with using SuperDARN (Hankasalmi) data. We consider events when the simultaneous EISCAT 42m and GPS data were available for the years 2010–2017, and in this paper we present, in detail, typical examples describing the overall picture, and we present the statistics for 120 events. We considered the dayside/cusp precipitation, substorm precipitation, daytime and nighttime PCPs, and precipitation associated with the interplanetary shock wave arrival. We demonstrate that substorm-associated precipitation (even without PCPs) can lead to a strong GPS phase (σϕ) scintillations up to ∼ 1.5–3 radians, which is much stronger than those usually produced by other types of considered ionosphere disturbances. The value of the substorm-phase scintillations in general correlate with the value of the geomagnetic field disturbance. But sometimes even a small geomagnetic substorm, when combined with the PCPs, produces quite strong phase scintillations. Cusp phase scintillations are lower than dayside PCPs scintillations. PCPs can lead to stronger ROT (rate of total electron content) variations than other types of ionosphere disturbances. So our observations suggest that the substorms and PCPs, being different types of the high-latitude disturbances, lead to the development of different types and scales of ionospheric irregularities.
Palmroth, Minna; Grandin, Maxime; Sarris, Theodoros E.; Doornbos, Eelco; Tourgaidis, Stylianos & Aikio, Anita [Show all 35 contributors for this article] (2021). Lower-thermosphere–ionosphere (LTI) quantities: current status of measuring techniques and models. Annales Geophysicae. ISSN 0992-7689. 39(1), p. 189–237. doi: 10.5194/angeo-39-189-2021. Full text in Research Archive Show summary
The lower-thermosphere–ionosphere (LTI) system consists of the upper atmosphere and the lower part of the ionosphere and as such comprises a complex system coupled to both the atmosphere below and space above. The atmospheric part of the LTI is dominated by laws of continuum fluid dynamics and chemistry, while the ionosphere is a plasma system controlled by electromagnetic forces driven by the magnetosphere, the solar wind, as well as the wind dynamo. The LTI is hence a domain controlled by many different physical processes. However, systematic in situ measurements within this region are severely lacking, although the LTI is located only 80 to 200 km above the surface of our planet. This paper reviews the current state of the art in measuring the LTI, either in situ or by several different remote-sensing methods. We begin by outlining the open questions within the LTI requiring high-quality in situ measurements, before reviewing directly observable parameters and their most important derivatives. The motivation for this review has arisen from the recent retention of the Daedalus mission as one among three competing mission candidates within the European Space Agency (ESA) Earth Explorer 10 Programme. However, this paper intends to cover the LTI parameters such that it can be used as a background scientific reference for any mission targeting in situ observations of the LTI.

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Pedersen, Christina Alsvik; Njåstad, Birgit; Aas, Wenche; Darelius, Elin Maria K.; Descamps, Sebastien & Flått, Stig [Show all 12 contributors for this article] (2026). Sustained Observations from Dronning Maud Land: The TONe Infrastructure. Full text in Research Archive
Jin, Yaqi; Spicher, Andres; Pecseli, Hans Laszlo; Clausen, Lasse; Miloch, Wojciech Jacek & Jacobsen, Knut Stanley [Show all 9 contributors for this article] (2024). In-situ observations of plasma blob inside the nightside auroral region and features of small-scale irregularities. Full text in Research Archive
Spicher, Andres; Kvammen, Andreas; Zettergren, Matthew David; Bonnell, John W.; Clausen, Lasse & Deshpande, Kshitija [Show all 14 contributors for this article] (2024). Understanding the creation of ionospheric F-region turbulence and its spatio-temporal evolution using GNSS scintillations, auxiliary instruments and modeling. Full text in Research Archive Show summary
The high-latitude F-region ionosphere is highly dynamic due to its strong coupling with the solar wind and magnetosphere. As a consequence, plasma density fluctuations or “irregular turbulent” structures are regularly observed in that region. When spanning a few decameters to a few kilometers, these irregularities can cause rapid fluctuations or “scintillations” in radio signals such as those typically used for trans-ionospheric navigation and communication, including Global Navigation Satellite Systems (GNSS) or HF communication systems. This work is intended to advance our understanding of the creation of ionospheric F-region turbulence and its spatio-temporal evolution. We show observations of the ionospheric conditions related to the presence of scintillations in the dayside region using measurements from ground-based instruments such as the EISCAT radars, all-sky cameras, and GNSS receivers combined with in-situ measurements from satellites and sounding rockets. We evaluate the possible sources of free energy and the relevance of several instabilities to create the irregularities causing the scintillations observed for selected case events. We focus on density structures related to flow shears and take advantage of the multi-instrument observations as input parameters for numerical simulations. We use the Geospace Environment Model of Ion-Neutral Interactions (GEMINI) [1] to characterize the nature of density fluctuations associated with the Kelvin-Helmholtz instability, with focus on the non-linear regime. Modelling results show that KHI can grow within minutes and can generate structures that lead to significant scintillations [2]. Additionally, we study how the density fluctuations evolve and how the energy is re-distributed across the scales as the instability evolves, allowing to compare with observations. Finally, we discuss future modelling work and observations necessary to make progress in the field. [1] Zettergren, et al. (2015), Geophys. Res. Lett., 42, 10, doi:10.1002/2015GL066806. [2] Spicher, et al. (2020), J. Geophys. Res., 125, e2019JA027734. https://doi.org/10.1029/2019JA027734
Spicher, Andres; Rexer, Theresa; Kvammen, Andreas; Madhanakumar, Mahith; Zettergren, M. & Oksavik, Kjellmar [Show all 11 contributors for this article] (2024). Characterization and Assessment of Structuring Connected to Auroral Dynamics using EISCAT_3D (CASCADE): A brief overview. Full text in Research Archive
Spicher, Andres; Kvammen, Andreas; Zettergren, M.; Roglans, Roger; Bonnell, John W & LaBelle, James [Show all 20 contributors for this article] (2024). Characterizing ionospheric turbulence on the poleward side of the cusp using sounding rocket observations and modelling work. Full text in Research Archive
Pedersen, Christina Alsvik; Njåstad, Birgit; Aas, Wenche; Chiche, Elin Maria Kristina Darelius; Descamps, Sebastien & Flått, Stig [Show all 13 contributors for this article] (2024). The Troll Observing Network (TONe): A contribution to improving observations in the data-sparse region of Dronning Maud Land, Antarctica. Full text in Research Archive
Sinevich, A.A.; Chernyshov, A.A.; Chugunin, D.V.; Miloch, Wojciech Jacek & Mogilevsky, M.M. (2024). Erratum to: The Polarization Jet/SAID and Plasma Irregularities of Different Scales (Bulletin of the Russian Academy of Sciences: Physics, (2024), 88, 3, (375-380), 10.1134/S1062873823705548). Bulletin of the Russian Academy of Sciences: Physics. ISSN 1062-8738. 88(11), p. 1863–1863. doi: 10.1134/S1062873824110030. Full text in Research Archive
Pedersen, Christina Alsvik; Schweitzer, Johannes; Njåstad, Brigit; Miloch, Wojciech Jacek; Aas, Wenche & Hudson, Stephen [Show all 12 contributors for this article] (2023). The New Norwegian Infrastructure - Troll Observing Network - under Establishment in Dronning Maud Land, Antarctica. Full text in Research Archive Show summary
Antarctica and the Southern Ocean are important parts of the Earth system. The physical and biological properties here to a large degree control and shape other parts of the Earth through atmospheric, cryospheric and oceanic connections. The Troll Observing Network – TONe - is a new comprehensive infrastructure centered around the Norwegian Troll Research Station in Dronning Maud Land. It will be an important contribution to global research efforts in this part of Antarctica, closing data gaps in Antarctic environmental observations and providing key data required to respond to the fundamental societal challenges and uncertainties facing the world today. The Norwegian and international partner consortium in TONe is in the process to develop the state-of-the-art, multi-platform, multi-disciplinary observatory network for environmental observations, and a remotely piloted aerial system (RPAS) services to collect data for studying and monitoring the atmosphere, terrestrial and marine environment. The observatory network consists of 8 observatories: an integrated cloud observatory, an atmosphere composition observatory, an infrasound array, an ionospheric observatory, a seismic array, an ice-shelf observatory, a multidisciplinary open ocean moored observatory and a sea-bird observatory. The key aspect of TONe is to ensure wide and free access to the data from the observatories and the RPAS services to the entire national and international research community. TONe as a whole will be implemented and fully operational from 2027, while single parts of the infrastructure will be available before that.
Pedersen, Christina Alsvik; Njåstad, Birgit; Descamps, Sebastien; Hattermann, Tore; Hudson, Stephen & Flått, Stig [Show all 11 contributors for this article] (2023). Troll observing network – for useful new data about Antarctica. Fram Forum. ISSN 1893-5532. 12, p. 120–125. Full text in Research Archive
Enengl, Florine; Marholm, Sigvald; Adhikari, Sayan; Marchand, Richard & Miloch, Wojciech Jacek (2023). Electron Temperature Inference from Fixed Bias Langmuir Probes Set-Ups in Ionospheric Conditions. Full text in Research Archive
Spicher, Andres; Kvammen, Andreas; LaBelle, James; Zettergren, Matthew D.; Bonnell, John W. & Roglans, Roger [Show all 20 contributors for this article] (2023). Examining the relevance of different instability mechanisms in causing ionospheric cusp irregularities based on sounding rocket data and numerical simulations. Full text in Research Archive
Enengl, Florine; Spogli, Luca; Kotova, Daria; Jin, Yaqi; Oksavik, Kjellmar & Partamies, Noora [Show all 7 contributors for this article] (2023). On the formation of small-scale irregularities driven by auroral particle precipitation. Full text in Research Archive
Enengl, Florine; Marholm, Sigvald; Adhikari, Sayan; Marchand, Richard & Miloch, Wojciech Jacek (2023). Electron Temperature Inference from Fixed Bias Langmuir Probes Set-Ups in Ionospheric Conditions. Full text in Research Archive
Kotova, Daria; Sinevich, A. A.; Chernyshov, Alexander A.; Chugunin, Dmitry V. & Miloch, Wojciech Jacek (2023). Effect of SAID on the Development of Ionospheric Scintillations and Irregularities in the Subauroral Region. Full text in Research Archive Show summary
The polarization jet, which is also known as the subauroral ion drift (SAID), is related to fast westward ion drifts. SAID is one of the main signatures of a geomagnetic disturbance in the subauroral ionosphere at the altitudes of the F-layer. SAID is a projection of the plasmapause onto the altitudes of the ionosphere, mainly during substorm periods when the AE index reaches more than 500 nT. SAID is characterized by a narrow jet (about 2º) and can have a duration of about several hours (in longitude). Plasma speed in SAID can reach several kilometers per second. Such high plasma velocities can lead to ionospheric scintillations affecting trans-ionospheric radio signals. For example, when radio signals of the Global Navigation Satellite System (GNSS) pass through ionospheric irregularities, receivers on the ground can observe rapid fluctuations in amplitude and/or phase of the incoming wave. These fluctuations can lead to serious deterioration of radio communication or navigational services. In this work, we analyze the possible influence of a polarization jet/SAID on the development of ionospheric scintillations and irregularities in the subauroral region. We consider the geomagnetic event on March 18, 2018 (with Kp = 6 and SYM-H = −53 nT), when according to the DMSP satellite data, a polarization jet/SAID was observed close to two GNSS Ionospheric Scintillation and TEC Monitor (GISTM) receivers in Antarctica (SANAE IV and Troll stations). For a more complete analysis, we also use data from nearby magnetometers at the Neumayer and SANAE IV stations, Super Dual Auroral Radar Network (SuperDARN) at SANAE IV, as well as from the Swarm and Norsat-1 satellites during considered substorm activity. We conclude that at the moment of auroral activity intensification, an increase in the magnitude of phase scintillation index (σφ) was observed in the region of the polarization jet/SAID in the subauroral ionosphere indicating high structuring of the ionospheric plasma. DK, WM acknowledge funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (ERC Consolidator Grant agreement No. 866357, POLAR-4DSpace). The work of ААS and AAC was supported by the Theoretical Physics and Mathematics Advancement Foundation "BASIS".
Chugunin, Dmitry V.; Kotova, Daria; Sinevich, A. A.; Chernyshov, Alexander A. & Miloch, Wojciech Jacek (2023). Scintillations of GNSS receivers in the subauroral region in the southern hemisphere. Full text in Research Archive Show summary
The work studies the possible influence of a polarization jet/SAID (SubAuroral ion Drift) on the phase scintillations of GNSS receivers. We consider the geomagnetic case of March 18, 2018, when, according to the DMSP satellite data, a polarization jet/SAID was observed over the area of Antarctica, where two GNSS receivers were located. For a more complete analysis, this study also uses Super Dual Auroral Radar Network (SuperDARN) observations as well as Swarm and Norsat-1 satellite data for this geomagnetic substorm. From the analysis of the data, it is concluded that at the moment of auroral activity intensification, an increased intensity of phase scintillations was observed in the region of the polarization jet/SAID in the subauroral ionosphere.
Kotova, Daria; Jin, Yaqi & Miloch, Wojciech Jacek (2022). Erratum: Interhemispheric variability of the electron density and derived parameters by the Swarm satellites during different solar activity (J. Space Weather Space Clim. (2022) 12 (12) DOI: 10.1051/swsc/2022007). Journal of Space Weather and Space Climate. 12. doi: 10.1051/swsc/2022013. Full text in Research Archive
Buschmann, Lisa Marie; Spicher, Andres; Clausen, Lasse; Marholm, Sigvald & Miloch, Wojciech Jacek (2022). Role of particle precipitation on plasma structuring at different altitudes by in-situ measurements. Full text in Research Archive
Miloch, Wojciech Jacek; Alfonsi, Lucilla; Spogli, Luca; Urbar, Jaroslav; Cesaroni, Claudio & Cicone, Antonio [Show all 15 contributors for this article] (2022). Swarm – VIP: Variability of Ionospheric Plasma studied and modelled based on data from the Swarm satellites. Full text in Research Archive
Jin, Yaqi; Miloch, Wojciech Jacek; Alfonsi, Lucilla; Spogli, Luca; Urbar, Jaroslav & Cesaroni, Claudio [Show all 13 contributors for this article] (2022). Variability of Ionospheric Plasma studied and modelled based on data from the Swarm satellites. Full text in Research Archive
Kotova, Daria; Jin, Yaqi; Spogli, Luca; Wood, Alan G.; Urbar, Jaroslav & Rawlings, James T. [Show all 11 contributors for this article] (2022). Electron density fluctuations from Swarm as a proxy for ground-based scintillation data: A statistical perspective. Full text in Research Archive
Miloch, Wojciech Jacek; Kotova, Daria & Jin, Yaqi (2022). Ionospheric plasma structuring over Antarctica based on satellite and ground observations. Full text in Research Archive
Miloch, Wojciech Jacek; Kotova, Daria; Lybekk, Bjørn & Trondsen, Espen (2022). Space weather studies at the Troll Ionospheric Observatory in Dronning Maud Land, Antarctica. Full text in Research Archive
Miloch, Wojciech Jacek (2022). The future of ionospheric research in Antarctica. Full text in Research Archive
Miloch, Wojciech Jacek (2022). Ionosfæreobservatoriet. Full text in Research Archive
Enengl, Florine; Kotova, Daria; Jin, Yaqi; Clausen, Lasse & Miloch, Wojciech Jacek (2022). Ionospheric plasma irregularities in relation to dynamic auroral forms. Full text in Research Archive
Kotova, Daria; Jin, Yaqi; Brask, Steffen Mattias; Spogli, Luca; Wood, Alan G. & Miloch, Wojciech Jacek (2022). Comparison of electron density fluctuations measured by Swarm satellites with the ground-based scintillation data. Full text in Research Archive
Spicher, Andres; LaBelle, James William; Bonnell, John W.; Roglans, Roger; Moser, Chrystal & Fuselier, Stephen A. [Show all 18 contributors for this article] (2022). Sounding rocket investigation of multi-scale (density) irregularities in the cusp region. Full text in Research Archive
Kotova, Daria; Jin, Yaqi & Miloch, Wojciech Jacek (2022). Interhemispheric investigation of variability of ionospheric parameters measured by the Swarm satellites for quiet geomagnetic conditions. Full text in Research Archive Show summary
The use of satellite data allows us to study the variability of ionospheric plasma parameters globally without references to ground stations or receivers in different regions of the Earth. The Swarm mission, which was launched in November 2013 and is still operational, allows us to investigate the effects of decreasing solar activity on ionospheric variability. We use the Swarm in-situ measurements of the electron density and derived parameters that have been combined into a unique dataset called the Ionospheric Plasma IRregularities product (IPIR) [1]. IPIR provides characteristics of the plasma variability along the orbit and gives information on plasma density structures in the ionosphere in terms of their amplitudes, gradients and spatial scales. In this study, we focused on distributions and statistics of these parameters in the Northern and Southern hemispheres for quiet geomagnetic conditions. Our results provide information on the shape of the distribution and probability density functions of electron density and derived ionospheric parameters that can be used as a baseline important for other modeling studies. Understanding the distribution of such parameters in the context of the geomagnetic activity and selected ionospheric regions can have implications for the development of new satellite instruments and for the accuracy of GNSS precise positioning. This work was supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (ERC Consolidator Grant agreement No. 866357, POLAR-4DSpace).
Kotova, Daria; Jin, Yaqi; Spogli, Luca; Wood, Alan G.; Alfonsi, Lucilla & Urbar, Jaroslav [Show all 9 contributors for this article] (2022). Comparison Of Electron Density Fluctuations From Swarm Satellites With The Ground-based Scintillation Data: A Statistical Perspective. Full text in Research Archive Show summary
The Swarm satellite mission is actively used to conduct various studies of the ionosphere, focusing on such aspects as the electric and magnetic fields or plasma temperature, structuring and irregularities. The mission is a constellation of three satellites that were launched in November 2013 and have been collecting data continuously since then. We use a global product based on the Swarm satellite measurements that characterizes ionospheric irregularities and fluctuations. The IPIR (Ionospheric Plasma IRregularities product) provides in-situ characteristics of plasma density structures in the ionosphere, of plasma irregularities in terms of their amplitudes, gradients and spatial scales and assigns them to geomagnetic regions. Ionospheric irregularities and fluctuations are often the cause increases the error in position, velocity, time determination based on Global Navigation Satellite Systems (GNSS), which signals pass through the ionosphere. The IPIR provides an indication, in the form of a numerical value index, on severity of irregularities for the integrity of trans-ionospheric radio signals and hence the accuracy of GNSS precise positioning. This work demonstrates that data from the Swarm satellite's flyby height can be used as a proxy for ground-based scintillation data. We compare two datasets from Swarm satellites (with 1-second resolution) and from groundbased scintillation receivers (with 1-minute resolution). To consider the measured parameters for the same area, we find time intervals when the Swarm satellites pass over the field of view of the ground-based Global Positioning System (GPS) receiver. A geometry with an elevation angle of 30° above the receiver was used to calculate these passes. We also performed an azimuthal selection of the GNSS data according to Swarm satellite fly. We used only those GPS satellites that flew near the position of the Swarm satellite in azimuth sector ±10°. We provide validations of the IPIR product against the ground-based measurements, focusing on GPS TEC and scintillation data in low and high-latitudes regions in different longitudinal sectors. We calculate median, mean, maximum and standard deviation values for parameters for both dataset for each conjunction point (for each GPS satellite and Swarm). We observe a weak trend of stronger scintillations with an increasing IPIR index, where the IPIR index presents a product of amplitudes and temporal variations in plasma densities.
Kotova, Daria; Jin, Yaqi & Miloch, Wojciech Jacek (2021). Investigation of interhemispheric variability of ionospheric parameters by the Swarm satellites for different solar activity. Full text in Research Archive Show summary
The use of satellite data allows us to study the variability of ionospheric plasma parameters globally without references to ground stations or receivers in different regions of the Earth. The Swarm mission, which was launched in 2014 and is still operational, allows us to investigate the effects of decreasing solar activity on the ionospheric variability. In our study, we use the Swarm in-situ measurements of the electron density and derived parameters. This dataset provides characteristics of the plasma variability along the orbit and gives information on plasma density structures in the ionosphere in terms of their amplitudes, gradients and spatial scales. In this study, we focused on the investigation of variability of these parameters in northern and southern hemispheres. Understanding of the distribution of such parameters in the context of the solar activity level and selected ionospheric regions can have implications for the development of new satellite instruments and for the accuracy of GNSS precise positioning.
Kotova, Daria & Miloch, Wojciech Jacek (2021). Study of the GNSS phase scintillation associated with auroral activity over Queen Maud Land, Antarctica. Full text in Research Archive Show summary
This study uses the dataset from the all-sky camera and the ground-based TEC and scintillation receiver installed in Antarctica at the Norwegian Research Station Troll. The station is located just on the equatorward edge of the quiet auroral oval. Thus, the observatory is in an optimal location to study the ionospheric response to geomagnetic disturbances. The all-sky camera was calibrated. In addition, we use geomagnetic indices and information about the solar wind from NASA's OMNIWeb Service, in-situ data onboard low Earth orbiting satellites (Defense Meteorological Satellite Program (DMSP), Swarm mission), and the Super Dual Auroral Radar Network (SuperDARN). Together with the ground-based GNSS scintillation receiver, a comprehensive analysis of the reasons for observing scintillations over the Troll station during the period of geomagnetic disturbances was carried out. The relationship between the activation of aurora and severe phase scintillations is shown.
Spicher, Andres; Moen, Jøran Idar; LaBelle, James William; Bonnell, John W; Roglans, Roger & Moser, Chrystal [Show all 18 contributors for this article] (2021). Sounding rocket studies of ionospheric turbulence above Svalbard. Full text in Research Archive Show summary
Every morning between about 06 UT and 11 UT, Svalbard rotates just below the cusps (dayside aurora), where direct coupling between the solar wind, magnetosphere and ionosphere occurs. This provides a unique window to study the dayside aurora and the highly dynamic processes associated with it, examples of which include electron and ion precipitation and heating, electrostatic and electromagnetic waves, as well as turbulence. In this work, we focus on the turbulence which, alongside with being of pure scientific interest, can also have societal impacts. Indeed, the “irregular” electron density structures associated with it can affect our technology infrastructures by for instance degrading High Frequency (HF) communication and Global Navigation Satellite Systems (GNSS) signals. After briefly reviewing some of the mechanisms believed to be important in the development of turbulence in the high-latitude ionosphere, we present recent observations of density irregularities obtained by sounding rockets above Svalbard. We focus on measurements made as a part of the Grand Challenge Initiative (GCI) Cusp, an international project combining sounding rockets missions and ground-based instruments to study the cusps. We show detailed characterization of the nature of the irregularities including their phase velocity and wavelengths, helping shedding light onto the process(es) involved in their formation, especially at the scales important for Space weather applications.
Mare, Francesca Di; Spicher, Andres; Clausen, Lasse; Miloch, Wojciech Jacek; Takahashi, Toru & Moen, Jøran Idar (2021). Turbulence and Intermittency in the Winter Cusp Ionosphere studied with the ICI Sounding Rockets. Full text in Research Archive
Adhikari, Sayan; Mukherjee, Rupak; Marholm, Sigvald & Miloch, Wojciech Jacek (2021). Development of a Deep Neural Network Model for Spacecraft Charging. Full text in Research Archive Show summary
A Deep Neural Network (DNN) model using the kinetic Particle-in-Cell (PIC) simulation data for spacecraft charging has been developed. The model will be able to predict the potential structure around the spacecraft based on the system parameters of any given system with certain accuracy. DNN provides an excellent tool where we could leverage deep learning for all machine learning tasks and expect better performance with surplus data availability. The usability of DNN is unlimited if a user can train such a model with physics-based parameters. In recent studies, it has shown promising outcomes in terms of accurate prediction of physical quantities[1-2]. In the present work, we used Tensorflow[3], a deep learning library, to classify the PIC simulation datasets. Using Tensorflow, we have compared the effects of multiple activation functions on classification results and developed a library for a case study. This work shows that integrating DNN into traditional computational methods might be the new beginning of developing next-generation modeling.
Spicher, Andres; Moen, Jøran Idar; Rowland, Douglas E.; LaBelle, James William; Kletzing, Craig A. & Blix, Kolbjørn [Show all 7 contributors for this article] (2021). Sounding rocket studies above Svalbard: the grand challenge initiative cusp. Full text in Research Archive
Miloch, Wojciech Jacek (2021). Ground based and in-situ studies of the polar ionosphere. Full text in Research Archive
Miloch, Wojciech Jacek; Alfonsi, Lucilla; Spogli, Luca; Urbar, Jaroslav; Cesaroni, C & Cicone, Antonio [Show all 14 contributors for this article] (2021). Variability of ionosphere studied and modelled based on data from the Swarm satellites. Full text in Research Archive
Holen, Gaute Arnesson; Miloch, Wojciech Jacek & Mishra, Rinku (2026). Plasma-object interaction in plasma environments: Numerical studies of spacecraft charging, probe accuracy and complex plasma. Universitetet i Oslo. Full text in Research Archive Show summary
The majority of space is made up of a sea of plasma, with island of solid matter such as planets, moons, dust, spacecraft or even astronauts. Immersing any solid object in plasma results in electric charging of the object, as well as significant disturbances to the surrounding plasma. Understanding the plasma-object interaction is crucial for many situations, including reliable operation of scientific instrumentation on sounding rockets and satellites. This thesis has developed a complementary set of numerical codes to simulate and study the plasma-object interaction. These codes were used to simulate sounding rockets, probes and daughter-payloads in the ionosphere, as well as the lunar surface and ensembles of dust particles, allowing us to study the plasma-object interaction from different perspectives. We uncover a new trapping mechanism for ions in magnetized plasma interacting with an object using a new analytical approach and validate the daughter-payload instrumentation on the ICI-5b sounding rocket mission. Simulations of dusty plasmas show that its spatial and temporal evolution and resulting dust structure is sensitive to small charge changes. Our studies provide new insights to the complex dynamics of objects in plasma, both for specific applications and for the fundamental understanding of objects in plasma.
Ros, Inés Eleonor Santandreu; Røed, Ketil & Miloch, Wojciech Jacek (2025). Experimental Characterization and Analysis of an Electron Emitter for Spacecraft Applications. Investigating the Role of Electron Emission in Spacecraft Surface Charge Control. Universitetet i Oslo. Full text in Research Archive Show summary
This master's thesis aims to characterize an electron emitter designed to control spacecraft charging. The primary objective of the emitter is to mitigate surface charging on the spacecraft, as the resulting potential differences can adversely affect both the experimental measurements taken by instruments such as the multi-Needle Langmuir Probe in relation to the plasma environment, and the performance of onboard electronics. The experimental approach involves placing a bulb filament, heated by applying a specific voltage, inside a vacuum chamber. The heated filament ejects electrons via thermionic emission, thereby functioning as an electron emitter. To quantify the emitted electrons, they are collected as a current using a Faraday cup. The Faraday cup is set to a specific acceleration potential to attract and collect as many electrons as possible. The aim is to identify configurations that effectively achieve the primary objective of this thesis. For this purpose, various experimental setups were used to obtain emitted current data.
Brask, Steffen Mattias; Miloch, Wojciech Jacek; Miyake, Yohei & Usui, Hideyuki (2024). Numerical Study of Langmuir Probes: Improving Accuracy Using PIC Simulations. Universitetet i Oslo. Full text in Research Archive Show summary
Did you know that in the vacuum of space, there is no vacuum? In fact, most of space is filled with charged particles in a plasma state. Close to Earth, Geomagnetic phenomena, space weather, and radio interference such as GPS scintillation are all explained with plasma dynamics. Space is also the largest laboratory we have for plasma physics. It is, therefore, no surprise that accurate measurements of the surrounding plasma of a spacecraft are a part of the foundation for understanding our own ionosphere. A common approach to probing a plasma is with Langmuir probes, which are conducting objects that collect an electrical current, from which we can infer plasma parameters, usually using orbital-motion-limited (OML) theory. It is known that OML will be erroneous under certain conditions. However, due to the complexity and scales of the problem, several sources of error have not been adequately studied and are therefore not well understood or accounted for. In this dissertation, we use Particle-in-Cell simulations to further our understanding by uncovering limits to the idealized OML theory and building models to correct several such error sources. The thesis focuses on charged-neutral collisional effects, the effects of imperfect geometries, and probes in magnetized plasmas.
Miloch, Wojciech Jacek; Clausen, Lasse; Jin, Yaqi & Enengl, Florine (2023). Investigation of Ionospheric Plasma Structuring and Processes related to Auroral Particle Precipitation. Universitetet i Oslo. Full text in Research Archive Show summary
Radio-waves propagating through the ionised part of the atmosphere, the ionosphere, can get impacted by plasma structures and irregularities. The effects on the signal can be observed by ground based receivers, and are indications of plasma structures the disturbed signal encountered. In this thesis, the aim is to understand how energetic particles precipitating into the ionosphere from space are related to plasma structuring and radio wave propagation disturbances. The signature of particle precipitation are auroral emissions. Auroral emissions are observed by all-sky cameras, with filters for different wavelengths. Studying how the aurora moves in space and time and in relation to it, how signal disturbances evolve in space and time, allows to gain understanding of plasma structuring and instabilities in the ionosphere. To classify plasma instabilities in detail, measurements of plasma parameters, such as electron density and temperature, are required. Commonly used instruments to measure them are Langmuir probes. In this thesis, a method was developed using machine learning, to infer electron temperature measurements at the sampling resolution of the instrument. The topics addressed in this thesis are important for future space weather services, and in particular reliability of the satellite based positioning services.

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Published Sep. 9, 2011 3:31 PM - Last modified Sep. 10, 2025 7:13 AM

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Plasma and space physics