Lasse Clausen

• Carter, Jennifer A.; Swamy, B. Narasimha; Lepri, S. T.; Raines, J. M.; Eastwood, J. P. & Samara-Ratna, P. [Show all 42 contributors for this article] (2026). Elfen: a mission to measure the heavy ion composition of the Earth’s magnetosphere. RAS Techniques and Instruments (RASTI). 5, p. 1–23. doi: 10.1093/rasti/rzag064. Full text in Research Archive
• Retselis, Anastasios-Faidon; Knutsen, Elise Wright; Holdcroft, Sam; Viet, Shayla; Wahlén, Rebecka & Virdis, Mario [Show all 19 contributors for this article] (2026). CENSSAT-1: A space weather mission and an educational platform. In Detrell, Gisela; Alarcia, Ramón María García; Messina, Vincenzo & Kinnaird, Alexander (Ed.), Proceedings of the 5th Symposium on Space Educational Activities (SSEA). Technical University of Munich. p. 852–857. doi: 10.14459/2026MD1857465. Full text in Research Archive Show summary

  The Symposium on Space Educational Activities (SSEA), organised by the European Space Agency’s Education Office, provides a forum for university students, professionals working in education, and other professionals in industry or agencies to present and discuss their experiences organising, running and/or participating in Educational Activities related to Space. After successful past events in Padova (2015), Budapest (2018), Leicester (2019), and Barcelona (2022), the 5th SSEA was held in April 2026 (the 8th, 9th, and 10th) in the TUM Aerospace Campus in Willy-Messerschmitt-Strasse 5, Taufkirchen, Germany. The local organisation team was led by the Technical University of Munich (TUM), involving Professors, PostDocs, PhD Candidates, and Master’s and Bachelor’s students, in close collaboration with the Bavarian aerospace ecosystem partners.

• 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.

• 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).

• Alzaabi, Mohammed; Burtz, Louis-Jerome; Amilineni, Santhosh; Almesmar, Sultan; Khoory, Mohammed S. & Albalooshi, Mohammad [Show all 13 contributors for this article] (2024). Operational Concepts and Rehearsal Results of the First Emirates Lunar Rover: Rashid-1. Space Science Reviews. ISSN 0038-6308. 220(8). doi: 10.1007/s11214-024-01118-6. Full text in Research Archive
• Ivarsen, Magnus Fagernes; St-Maurice, Jean-Pierre; Jin, Yaqi; Park, Jaeheung; Buschmann, Lisa Marie & Clausen, Lasse (2024). To what degree does a high-energy aurora destroy F-region irregularities? Frontiers in Astronomy and Space Sciences. 11. doi: 10.3389/fspas.2024.1309136. Full text in Research Archive Show summary

  Using two separate databases of in situ ionospheric observations, we present case studies and perform a statistical investigation of the link between energetic precipitating particles during the polar night and high-latitude F-region steepening density spectra. Our study covers approximately 3 years of data obtained near the peak of the 24th solar cycle from four Defense Meteorological Satellite Program satellites and from the European Space Agency’s Swarm satellites. Focusing on the midnight sector of the auroral oval, we found that there is a near-perfect co-location between high-energy precipitating particles and occurrence of dissipating F-region plasma density spectra. This is because the precipitating energy flux strongly enhances the E-region Pedersen conductivity, allowing fast and efficient dissipation of kilometer-scale F-region irregularities. Spectra that are possibly non-dissipating are in turn co-located with the distribution of soft electron precipitation. Together, dissipating and non-dissipating density spectra constitute two distinct irregularity regimes. Surprisingly, we also found that efficient dissipation notwithstanding, high-energy precipitating particles cause a net increase in the F-region irregularity power, suggesting that growth and dissipation are interlinked and that some of the observed F-region irregularities may conceivably be generated in the E region. This work is expected to be beneficial for the classification of F-region in situ density spectra and suggests that such density spectra can be used to infer the presence of high-energy or low-energy precipitations based on spectral properties.

• 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.

• 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.

• 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.

• 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.

• 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
• 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.

• Lessard, Marc R.; Damsell, Alec; Sadler, F. Brent; Oksavik, Kjellmar & Clausen, Lasse (2023). Interhemispheric asymmetries of neutral upwelling and ion upflow. Frontiers in Astronomy and Space Sciences. 10. doi: 10.3389/fspas.2023.1151016. Full text in Research Archive Show summary

  This work addresses interhemispheric differences in cusp-related neutral density enhancements. The focus is on enhancements that are driven by Poleward Moving Auroral Forms (PMAF), which provide a repetitive sequence of soft electron precipitation to the ionosphere. Because the time-scales of the resultant electron heating, ion upflow and neutral upwelling range from a few seconds to tens of minutes, i.e., longer than the time required for the thermosphere to return to its relaxed state, each subsequent PMAF encounters different initial conditions. With this in mind, our study investigates the role of a dark versus daylight ionosphere, using 3 different scenarios. The first case compares this effect during solar minimum at Longyearbyen, Svalbard, an ideal location for observing cusp dynamics. The second case addresses solar maximum at Longyearbyen and the third case compares Longyearbyen to its magnetically conjugate Zhongshan Station in Antarctica. We conclude 1) for each of the 3 scenarios ion upflow speeds, neutral upwelling speeds and neutral density enhancements are all significantly greater in a dark ionosphere, by perhaps as much as a factor or 2 or 3, relative to a sunlit ionosphere, 2) that upflowing ions are the driver of neutral upwelling via ion-neutral collisions (momentum transfer), with fast-moving ions transferring upward momentum to slow-moving neutrals, and 3) the ratios of neutral upflow speeds to ion upflow speeds, vnSunlit/viSunlit is the order of 0.07 for all stations (at 800 km) in the first and second cases studied, but only 0.02 at Zhongshan in the 3rd case studied, a factor of ∼3 less than the other locations. This is thought to be due to an increased thermospheric density at Zhongshan, which essentially provides a greater total mass for the upflowing ions to lift.

• Liu, Guangdong; Marholm, Sigvald; Eklund, Anders Johan; Clausen, Lasse & Marchand, Richard (2023). m-NLP Inference Models Using Simulation and Regression Techniques. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 128(2). doi: 10.1029/2022JA030835. Full text in Research Archive Show summary

  Current inference techniques for processing multi-needle Langmuir probe (m-NLP) data are often based on adaptations of the Orbital Motion-Limited (OML) theory which relies on several simplifying assumptions. Some of these assumptions, however, are typically not well satisfied in actual experimental conditions, thus leading to uncontrolled uncertainties in inferred plasma parameters. In order to remedy this difficulty, three-dimensional kinetic particle in cell simulations are used to construct a synthetic data set, which is used to compare and assess different m-NLP inference techniques. Using a synthetic data set, regression-based models capable of inferring electron density and satellite potentials from 4-tuples of currents collected with fixed-bias needle probes similar to those on the NorSat-1 satellite, are trained and validated. The regression techniques presented show promising results for plasma density inferences with RMS relative errors less than 20%, and satellite potential inferences with RMS errors less than 0.2 V for potentials ranging from −6 to −1 V. The new inference approaches presented are applied to NorSat-1 data, and compared with existing state-of-the-art inference techniques.

• Ivarsen, Magnus Fagernes; St‐Maurice, Jean-Pierre; Hussey, Glenn C.; Spicher, Andres; Jin, Yaqi & Lozinsky, Adam [Show all 10 contributors for this article] (2023). Measuring small-scale plasma irregularities in the high-latitude E- and F-regions simultaneously. Scientific Reports. 13. doi: 10.1038/s41598-023-38777-4. Full text in Research Archive Show summary

  The ionosphere, Earth’s space environment, exhibits widespread turbulent structuring, or plasma irregularities, visualized by the auroral displays seen in Earth’s polar regions. Such plasma irregularities have been studied for decades, but plasma turbulence remains an elusive phenomenon. We combine scale-dependent measurements from a ground-based radar with satellite observations to characterize small-scale irregularities simultaneously in the bottomside and topside ionosphere and perform a statistical analysis on an aggregate from both instruments over time. We demonstrate the clear mapping of information vertically along the ionospheric altitude column, for field-perpendicular wavelengths down to 1.5 km. Our results paint a picture of the northern hemisphere high-latitude ionosphere as a turbulent system that is in a constant state of growth and decay; energy is being constantly injected and dissipated as the system is continuously attempting an accelerated return to equilibrium. We connect the widespread irregularity dissipation to Pedersen conductance in the E-region, and discuss the similarities between irregularities found in the polar cap and in the auroral region in that context. We find that the effects of a conducting E-region on certain turbulent properties (small-scale spectral index) is near ubiquitous in the dataset, and so we suggest that the electrodynamics of a conducting E-region must be considered when discussing plasma turbulence at high latitudes. This intimate relationship opens up the possibility that E-region conductivity is associated with the generation of F-region irregularities, though further studies are needed to assess that possibility.

• 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.

• Takahashi, Toru; Spicher, Andres; Mare, Francesca Di; Rowland, Douglas E.; Pfaff, Robert F. & Collier, Michael R. [Show all 8 contributors for this article] (2022). Suppression of ionospheric irregularity due to auroral particle impact. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 127(1). doi: 10.1029/2020JA028725. Full text in Research Archive Show summary

  The VISIONS-2 35.039 sounding rocket was launched from Ny-Ålesund, Svalbard, on 7 December 2018 at 11:06 UT, and traveled overhead of the cusp aurora. The payload reached an apogee of 806.6 km and provided measurements of the electric field (E) and electron density (N_e ) with a high sampling rate of 6,250 Hz. The high-sampling-data make it possible to estimate the horizontal structure of E and Ne on scales ranging from meters to kilometers scale. The horizontal variation in the electron density and electric field (ΔN_e /N_e and ΔE) and integrated power of N_e and E (ΣP_Ne and ΣP_E) for 1–10, 10–100, and 100–1,000 Hz range were derived. The derived values were compared with the 557.7 and 630.0 nm emission intensities obtained from an all-sky camera installed in Ny-Ålesund projected at the footprint of the rocket, which was calculated by tracing the Earth's magnetic field line from the rocket altitude to the emission layer. ΔN_e /N_e , ΔE, ΣP_Ne, and ΣP_E increased with the 630.0 nm emission intensity. Of particular interest is the lower level irregularity was observed when the 557.7 nm emission intensity exceeded 4.5 kR compared with other time interval. This may suggest that particle impact ionization created sufficient Pedersen conductance in the E-region to short the F-region current. This short-circuit seemed to cause the suppression of the irregularities in the F-region and lower level irregularities were also observed in the rocket altitude.

• 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.

• 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.

• Billett, D.D.; McWilliams, K.A.; Perry, G.W.; Clausen, Lasse & Anderson, B.J. (2022). Ionospheric Energy Input in Response to Changes in Solar Wind Driving: Statistics From the SuperDARN and AMPERE Campaigns. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 127(3). doi: 10.1029/2021JA030102. Full text in Research Archive Show summary

  For over a decade, the Super Dual Auroral Radar Network and the Active Magnetosphere and Planetary Electrodynamics Response Experiment have been measuring ionospheric convection and field-aligned currents in the high-latitude regions, respectively. Using both, high-latitude maps of the magnetosphere-ionosphere energy transfer rate (the Poynting flux) have been generated with a time resolution of 2 min between 2010 and 2017. These data driven Poynting flux (PF) patterns are used in this study to perform a superposed epoch analysis of the northern hemisphere ionospheric response to transitions of the interplanetary magnetic field Bz component, upwards of 60° geomagnetic latitude. We discuss the difference in the distribution of PF between the magnetosphere-ionosphere Dungey cycle “switching on” and “switching off” to solar wind driving, revealing that they are not symmetric temporally or spatially.

• 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.

• Park, Jaeheung; Rajesh, P.K.; Ivarsen, Magnus Fagernes; Lin, Charles C. H.; Eastes, Richard W. & Chao, Chi Kuang [Show all 9 contributors for this article] (2022). Coordinated Observations of Rocket Exhaust Depletion: GOLD, Madrigal TEC, and Multiple Low-Earth-Orbit Satellites. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 127(2). doi: 10.1029/2021JA029909. Full text in Research Archive Show summary

  A plasma density hole was created in the ionosphere by a rocket launch from Cape Canaveral, Florida near local sunset on 30 August 2020, which is called rocket exhaust depletion (RED). The hole persisted for several hours into the night and was observed in total electron content (TEC) maps, the Global-scale Observations of the Limb and Disk (GOLD) imager, and multiple low-earth-orbit satellites. The RED created a nightglow pit in the GOLD 135.6 nm image. Swarm satellites found that the RED exhibited insignificant changes in electron/ion temperature and field-aligned currents. On the other hand, magnetic field strength was enhanced inside the RED by a few tenths of a nanotesla. Assimilation data products of the Constellation Observing System for Meteorology, Ionosphere, and Climate 2 (COSMIC-2) mission reveal that ionospheric slab thickness increased at the center of the RED, which is supported by combined analyses of the GOLD and TEC data. The RED did not host conspicuous substructures that are stronger and longer-lasting than the ambient plasma did.

• 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.

• 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.

• Follestad, Anna Kristine Fæhn; Clausen, Lasse; Moen, Jøran Idar & Jacobsen, Knut Stanley (2021). Latitudinal, Diurnal, and Seasonal Variations in the Accuracy of an RTK Positioning System and Its Relationship With Ionospheric Irregularities. Space Weather. 19(6). doi: 10.1029/2020SW002625. Full text in Research Archive Show summary

  The Norwegian Mapping Authority operates a network real time kinematic (RTK) system called CPOS, a positioning service providing centimeter level accuracy aimed at commercial users, for example, in civil engineering, excavation, and surveying. CPOS is based on multiple Global Navigation Satellite Systems (multi-GNSS) in addition to base stations to provide correction data. CPOS position accuracy is subject to disturbances arising from space weather phenomena, which can disturb and disrupt GNSS signals. Studies have shown that CPOS performance is sensitive to the presence of plasma irregularities, usually quantified by the rate of change of total electron content index (ROTI). This study investigates the performance of CPOS over a 3-year period, and its relationship with ionospheric irregularities. In a statistical analysis, we observe that CPOS position errors have seasonal, diurnal, and latitudinal variations. The most frequent position errors occur around magnetic noon and are of moderate severity, while the largest position errors occur around night-time, agreeing well with climatology studies on GNSS scintillations. Additionally, we investigate ionospheric irregularities as characterized by the rate of TEC index (ROTI). We find that there is a significant correlation between CPOS accuracy and ROTI, but that there are also other contributing factors.

• 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.

• Billett, Daniel; Gareth, Perry; Clausen, Lasse Boy Novock; Archer, William; McWilliams, Kathryn A. & Haaland, Stein Egil [Show all 11 contributors for this article] (2021). The Relationship Between Large Scale Thermospheric Density Enhancements and the Spatial Distribution of Poynting Flux. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 126(5). doi: 10.1029/2021JA029205. Full text in Research Archive Show summary

  Large thermospheric neutral density enhancements in the cusp region have been examined for many years. The Challenging Minisatellite Payload (CHAMP) satellite for example has enabled many observations of the perturbation, showing that it is mesoscale in size and exists statistically over solar cycle timescales. Further studies examining the relationship with magnetospheric energy input have shown that fine-scale Poynting fluxes are associated with the density perturbations on a case-by-case basis, whilst others have found that mesoscale downward fluxes also exist in the cusp region statistically. In this study, we use nearly 8 years of the overlapping Super Dual Auroral Radar Network and Active Magnetosphere and Planetary Electrodynamics Response Experiment datasets to generate global-scale patterns of the high-latitude and height-integrated Poynting flux into the ionosphere, with a time resolution of 2 min. From these, average patterns are generated based on the interplanetary magnetic field orientation. We show the cusp is indeed an important feature in the Poynting flux maps, but the magnitude does not correlate well with statistical neutral mass density perturbations observed by the CHAMP satellite on similar spatial scales. Importantly, the lack of correlation between mesoscale height-integrated Poynting fluxes and the cusp neutral mass density enhancement gives possible insight into other processes that may account for the discrepancy, such as energy deposition at finer scale sizes or at higher altitudes than captured.

• Chernyshov, Alexander A.; Chugunin, Dmitry V.; Frolov, Vladimor L.; Clausen, Lasse Boy Novock; Miloch, Wojciech Jacek & Mogilevsky, Mikhail M. (2020). In situ observations of ionospheric heating effects: First results from a joint SURA and NorSat-1 experiment. Geophysical Research Letters. ISSN 0094-8276. 47:e2020GL088462(13), p. 1–9. doi: 10.1029/2020GL088462. Full text in Research Archive Show summary

  This work presents the first results of measurements of artificial plasma disturbance characteristics using the low‐orbit NorSat‐1 satellite, which are excited when the ionospheric F2 layer is modified by powerful high‐frequency (HF) waves emitted by the SURA heating facility. NorSat‐1 carries the multineedle Langmuir probe instrument, which is capable of sampling the electron density at a nominal rate up to 1 kHz. The uniqueness of this experiment lies in the fact that the satellite passes very close to the center of the HF‐perturbed magnetic flux tube and in situ observations are first carried out in winter when the absorption is still small in the morning as the Sun is low above the horizon. There are HF‐induced plasma temperature and density variations at satellite altitudes of about 580 km. Plasma irregularities are detected by in situ measurements down to 200 m at the southern border of the SURA heating region.

• Jin, Yaqi; Xiong, Chao; Clausen, Lasse Boy Novock; Spicher, Andres; Kotova, Daria & Brask, Steffen [Show all 9 contributors for this article] (2020). Ionospheric Plasma Irregularities Based on In Situ Measurements From the Swarm Satellites. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 125(7). doi: 10.1029/2020JA028103. Full text in Research Archive Show summary

  In this study, we present global climatological distributions of ionospheric plasma irregularities based on measurements by the Swarm satellites. These first global statistics obtained by direct, in situ measurements of plasma variations with Swarm confirm the presence of three main regions of strong ionospheric irregularities: the magnetic equator extending from postsunset to early morning, in the auroral ovals (from dayside cusp to nightside), and inside the polar caps. At equatorial latitudes, ionospheric irregularities form two bands of enhanced plasma fluctuations centered around ±10° magnetic latitude. Due to different plasma processes, ionospheric irregularities at high and low latitudes show different distributions. Though the averaged intensity of plasma irregularities is weaker at equatorial latitudes than at high latitudes, the occurrence rate of significant plasma fluctuations (corresponding to extreme events) is much higher at the equator than that at high latitudes. Equatorial irregularities display clear seasonal and longitudinal variations; that is, they are most prominent over South America during the December solstice and are located over Africa during the June solstice. The magnitude of ionospheric irregularities at all latitudes is strongly controlled by the solar activity. Ionospheric irregularities become significantly weaker after 2016 during the current declining phase of solar activity. The interplanetary magnetic field Bz modulates the occurrence of ionospheric irregularities at both high and low latitudes.

• Lessard, Marc R.; Fritz, Bruce; Sadler, Brent; Cohen, Ian J.; Kenward, David & Godbole, Niharika [Show all 21 contributors for this article] (2020). Overview of the Rocket Experiment for Neutral Upwelling Sounding Rocket 2 (RENU2). Geophysical Research Letters. ISSN 0094-8276. 47(21), p. 1–7. doi: 10.1029/2018GL081885. Full text in Research Archive Show summary

  The Rocket Experiment for Neutral Upwelling 2 (RENU2) rocket was launched on 13 December 2015 at 07:34 UT. The payload transited the cusp region during a neutral upwelling event, supported by a comprehensive set of onboard and ground‐based instrumentation. RENU2 data highlight two important processes. One is that a proper understanding of neutral upwelling by Poleward Moving Auroral Forms (PMAFs) requires a treatment that mimics the quasiperiodic passage of a sequence of PMAFs. As a PMAF reaches a flux tube, its physical consequences must be determined including the residual history of effects from previous passages, implying that understanding such a process requires an accounting of the system hysteresis. Second, RENU2 observations suggest that neutral density enhancements driven by precipitation and/or Joule heating can be highly structured in altitude and latitude. In addition, timescales involving neutral dynamics suggest that the structuring must be slowly changing, for example, over the course of 10 to tens of minutes.

• Hwang, K.-J.; Nishimura, Yukitoshi; Coster, A.; Gillies, R.G.; Fear, R. C. & Fuselier, Stephen A. [Show all 20 contributors for this article] (2020). Sequential Observations of Flux Transfer Events, Poleward-Moving Auroral Forms, and Polar Cap Patches. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 125(6). doi: 10.1029/2019JA027674. Full text in Research Archive Show summary

  We report the observation of solar wind‐magnetosphere‐ionosphere interactions using a series of flux transfer events (FTEs) observed by Magnetospheric MultiScale (MMS) mission located near the dayside magnetopause on 18 December 2017. The FTEs were observed to propagate duskward and either southward or slightly northward, as predicted under duskward and southward interplanetary magnetic field (IMF). The Cooling model also predicted a significant dawnward propagation of northward‐moving FTEs. Near the MMS footprint, a series of poleward‐moving auroral forms (PMAFs) occurred almost simultaneously with those FTEs. They propagated poleward and westward, consistent with the modeled FTE propagation. The intervals between FTEs, relatively consistent with those between PMAFs, strongly suggest a one‐to‐one correspondence between the dayside transients and ionospheric responses. The FTEs embedded in continuous reconnection observed by MMS and corresponding PMAFs individually occurred during persistent auroral activity recorded by an all‐sky imager strongly indicate that those FTEs/PMAFs resulted from the temporal modulation of the reconnection rate during continuous reconnection. With the decay of the PMAFs associated with the FTEs, patch‐like plasma density enhancements were detected to form and propagate poleward and then dawnward. Propagation to the dawn was also suggested by the Super Dual Auroral Radar Network (SuperDARN) convection and Global Positioning System (GPS) total electron content data. We relate the temporal variation of the driving solar‐wind and magnetospheric mechanism to that of the high‐latitude and polar ionospheric responses and estimate the response time.

• Follestad, Anna Kristine Fæhn; Clausen, Lasse Boy Novock; Miloch, Wojciech Jacek; IJssel, J. van den & Haagmans, Roger (2020). Two-Dimensional Reconstruction of Ionospheric Plasma Density Variations Using Swarm. Space Weather. 18. doi: 10.1029/2019SW002406. Full text in Research Archive Show summary

  Space weather phenomena such as scintillations of Global Navigation Satellite Systems (GNSS) signals are of increasing importance for aviation, the maritime, and civil engineering industries. The ionospheric plasma irregularities causing scintillations are associated with strong gradients in ionospheric plasma density. To provide nowcasts and forecasts of space weather effects, it is vital to monitor the ionosphere and detect strong density variations. To reconstruct plasma density variations in the polar cap ionosphere, we use total electron content (TEC) estimates from the Swarm satellites' GPS receivers. By considering events where the Swarm satellites are in close proximity, we obtain plasma density variations by inverting TEC measurements on a two‐dimensional grid. We first demonstrate the method using synthetic test data, before applying it to real data. The method is validated using in situ Langmuir probe measurements and ground‐based TEC observations. We find that the new method can reproduce density variations, although it is sensitive to the geometry of the Swarm satellite constellation and to the calculated plasma temperature. Our proposed method opens new possibilities for ionospheric plasma monitoring that uses GPS receivers aboard low Earth orbit (LEO) satellites.

• Ivarsen, Magnus Fagernes; Park, Jaeheung; Kwak, Young-Sil; Jin, Yaqi; Knudsen, D. J. & Clausen, Lasse Boy Novock (2020). Observational Evidence for the Role of Hall Conductance in Alfvén Wave Reflection. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 125(12). doi: 10.1029/2020JA028119. Full text in Research Archive Show summary

  Electromagnetic energy carried by magnetohydrodynamic modes is an important mechanism in the energy transfer between the magnetosphere and the ionosphere. Alfvén waves are known to carry field‐aligned currents and thus play an important role in the dynamics of the ionosphere‐magnetosphere coupling. The role of Hall conductance in this interplay has been explored in magnetohydrodynamic models of the ionosphere but has hitherto not been observed in situ. We use 5 years of observations from the Swarm mission to shed light on this interplay. We present a high‐latitude climatology of both the measured Poynting flux and the measured Alfvén wave reflection coefficient. Our results indicate that high‐energy precipitation, which penetrates deep into the ionosphere and directly leads to strongly enhanced Hall conductance, is an important cause of positively interfering Alfvén wave reflection. We present such observational evidence and, with that, suggest that Hall conductance is substantially more important in the ionospheric wave reflection climatology than hitherto believed.

• Spicher, Andres; Deshpande, Kshitija; Jin, Yaqi; Oksavik, Kjellmar; Zettergren, Matthew D. & Clausen, Lasse Boy Novock [Show all 9 contributors for this article] (2020). On the Production of Ionospheric Irregularities Via Kelvin-Helmholtz Instability Associated with Cusp Flow Channels. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 125(6). doi: 10.1029/2019JA027734. Full text in Research Archive Show summary

  We present a multi‐instrument multiscale study of a channel of enhanced, inhomogeneous flow in the cusp ionosphere occurring on November 30, 2014. We provide evidence that strong Global Navigation Satellite System (GNSS) phase scintillations indices (σϕ>0.5 rad) can arise from such events, indicating that they are important in the context of space weather impacts on technology. We compare in detail two‐dimensional maps of ionospheric density, velocity, and temperatures obtained by the European Incoherent Scatter Scientific Association Svalbard Radar with scintillation indices detected from a network of four GNSS receivers around Svalbard and examine the different sources of free energy for irregularity creation. We observe that the strongest phase scintillations occur on the poleward side of the flow channel in a region of sheared plasma motion and structured low‐energy particle precipitation. As inhomogeneous plasma flows are evident in our observations, we perform a quantitative, nonlinear analysis of the Kelvin–Helmholtz instability (KHI) and its impact on phase scintillations using numerical simulations from the first principles‐based Geospace Environment Model of Ion‐Neutral Interactions and Satellite‐beacon Ionospheric‐scintillation Global Model of the upper Atmosphere. Using representative values consistent with the radar data, we show that KHI can efficiently create density structures along with considerable scintillations and is thus likely to contribute significantly under similar conditions, which are frequent in the cusp.

• Nishimura, Yukitoshi; Zhang, Shun-Rong; Lyons, Lawrence R.; Deng, Yue; Coster, Anthea J. & Moen, Jøran Idar [Show all 9 contributors for this article] (2020). Source Region and Propagation of Dayside Large-Scale Traveling Ionospheric Disturbances. Geophysical Research Letters. ISSN 0094-8276. 47(19). doi: 10.1029/2020GL089451. Full text in Research Archive
• Follestad, Anna Kristine Fæhn; Clausen, Lasse Boy Novock; Thomas, E.G.; Jin, Yaqi & Coster, A. (2019). Polar cap patch prediction in the expanding contracting polar cap paradigm. Space Weather. 17(11), p. 1570–1583. doi: 10.1029/2019SW002276. Full text in Research Archive Show summary

  Space weather can cause serious disturbances of global navigation satellite systems (GNSS) used for positioning and navigation purposes. This paper describes a new method to forecast space weather disturbances on GNSS at high latitudes, in which we describe the formation and propagation of polar cap patches and predict their arrival at the nightside auroral oval. The space weather prediction model builds on the expanding/contracting polar cap (ECPC) paradigm and total electron content (TEC) observations from the Global Positioning System (GPS) network. The input parameter is satellite observations of the interplanetary magnetic field at the first Lagrange point. To validate our prediction model, we perform a case study in which we compare the results from our prediction model to observations from the GPS TEC data from the MIT's Madrigal database, convection data from Super Dual Auroral radar network, and scintillation data from Svalbard. Our results show that the ECPC paradigm describes the polar cap patch motion well and can be used to predict scintillations of GPS signals at high latitudes.

• Ivarsen, Magnus Fagernes; Hoang, Huy Minh; Yang, Lei; Clausen, Lasse Boy Novock; Spicher, Andres & Jin, Yaqi [Show all 10 contributors for this article] (2019). Multineedle Langmuir Probe Operation and Acute Probe Current Susceptibility to Spacecraft Potential. IEEE Transactions on Plasma Science. ISSN 0093-3813. 47(8), p. 3816–3823. doi: 10.1109/TPS.2019.2906377. Full text in Research Archive Show summary

  NorSat-1 was launched on July 14, 2017 as a satellite carrying, among other instruments, the multineedle Langmuir probe (m-NLP), an instrument which, on NorSat-1, is capable of measuring the ionospheric plasma electron density with the high sampling frequency of 1000 Hz. The m-NLP instrument operates by analyzing the current-voltage diagram resulting from the measurements from each individual probe. In principle, the m-NLP operation methodology should be insensitive to spacecraft charging. However, this is not always the case. In this paper, we present an overview of the instrument response to passes into and out of eclipse. When the satellite exits eclipse, we observe a collapse in the collected probe currents. This acute drop is unaccounted for by the theoretical operation of the instrument. We present a statistical analysis of the phenomenon based on several months of NorSat-1 data, and we suggest a plausible reason for the observed drop in the current, namely, spacecraft charging, by solar cell arrays upon eclipse exit. We briefly discuss how satellite orientation and plasma wake affect the current drop. With this paper, we address Langmuir probe current susceptibility to spacecraft potential.

• Ivarsen, Magnus Fagernes; Jin, Yaqi; Spicher, Andres & Clausen, Lasse Boy Novock (2019). Direct Evidence for the Dissipation of Small-Scale Ionospheric Plasma Structures by a Conductive E Region. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 124(4), p. 2935–2942. doi: 10.1029/2019JA026500. Full text in Research Archive Show summary

  The conductivity of the ionospheric E region is known to cause effective dissipation of plasma structures in the F region. We use 3.5 years of 16‐Hz sampling rate electron density measurements from the Swarm advanced data set to investigate seasonal dependencies of plasma structure dissipation. Using a novel algorithm to infer plasma structure dissipation through detection of spectral breaks in density fluctuation power spectra, we analyze 100,000 spectra based on data from Swarm A in both the northern and southern polar caps. For the first time, we can present long‐term development of small‐scale (∼1‐10 km) plasma structure diffusion in the high‐latitude ionospheric F region. We discuss possible reasons for these variations. This study presents evidence for the E region as an important factor in the seasonal variation of F region plasma irregularity amplitudes.

• Hoang, Huy Minh; Røed, Ketil; Bekkeng, Tore Andre; Moen, Jøran Idar; Clausen, Lasse Boy Novock & Trondsen, Espen [Show all 16 contributors for this article] (2019). The Multi-needle Langmuir Probe Instrument for QB50 Mission: Case Studies of Ex-Alta 1 and Hoopoe Satellites. Space Science Reviews. ISSN 0038-6308. 215:21(2), p. 1–19. doi: 10.1007/s11214-019-0586-x. Full text in Research Archive Show summary

  The QB50 mission is a satellite constellation designed to carry out measurements at between 200–380 km altitude in the ionosphere. The multi-needle Langmuir probe (m-NLP) instrument has been mounted on board eleven QB50 satellites in order to characterize ambient plasma. The distinct feature of this instrument is its capability of measuring the plasma density at high spatial resolution without the need to know the electron temperature or the spacecraft potential. While the instrument has been deployed on many sounding rockets, the QB50 satellites offer the opportunity to demonstrate the operation of the instrument in low-earth orbit (LEO). This paper provides a brief review of the m-NLP instrument specifically designed for the QB50 mission and the case studies of the instrument’s performance on board the Ex-Alta 1 and Hoopoe satellites. The system has also been functionally verified in a plasma chamber at the European Space Research and Technology Center (ESTEC). Although the QB50 mission’s scientific goals have not been reached yet and some uncertainties still remain, there are some optimistic in-orbit preliminary results which could be helpful for the system improvement in future campaigns. Particularly, the electron emitter as part of the m-NLP science unit has demonstrated its capability in the plasma chamber and in orbit to mitigate spacecraft charging effects.

• Burleigh, Meghan R.; Zettergren, Matthew David; Lynch, Kristina A.; Lessard, Marc R.; Moen, Jøran Idar & Clausen, Lasse Boy Novock [Show all 9 contributors for this article] (2019). Transient Ionospheric Upflow Driven by Poleward Moving Auroral forms Observed During the Rocket Experiment for Neutral Upwelling 2 (RENU2) Campaign. Geophysical Research Letters. ISSN 0094-8276. 46(12), p. 6297–6305. doi: 10.1029/2018GL081886. Full text in Research Archive Show summary

  This study examines cumulative effects of a series of poleward moving auroral forms on ion upflow and downflow. These effects are investigated using an ionospheric model with inputs derived from the Rocket Experiment for Neutral Upwelling 2 (RENU2) sounding rocket campaign. Auroral precipitation inputs are constrained by all‐sky imager brightness values resulting in significant latitudinal structuring in simulated ionospheric upflows due to transient forcing. For contrast, a case with steady forcing generates almost double the O+ upflow transport through 1,000 km when compared to poleward moving auroral form‐like structures. At high altitudes, model results show a spread in upflow response time dependent on ion mass, with molecular ions responding slower than atomic ions by several minutes. While the modeled auroral precipitation is not strong enough to accelerate ions to escape velocities, source populations available for higher‐altitude energization processes are greatly impacted by variable forcing exhibited by the RENU2 event.

• Jin, Yaqi; Spicher, Andres; Xiong, Chao; Clausen, Lasse Boy Novock; Kervalishvili, Guram & Stolle, Claudia [Show all 7 contributors for this article] (2019). Ionospheric Plasma Irregularities Characterized by the Swarm Satellites: Statistics at High Latitudes. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 124(2), p. 1262–1282. doi: 10.1029/2018JA026063. Full text in Research Archive Show summary

  The polar ionosphere is often characterized by irregularities and fluctuations in the plasma density. We present a statistical study of ionospheric plasma irregularities based on the observations from the European Space Agency's Swarm mission. The in situ electron density obtained with the Langmuir probe and the total electron content from the onboard global positioning system receiver are used to detect ionospheric plasma irregularities. We derive the irregularity parameters from the electron density in terms of the rate of change of density index and electron density gradients. We also use the rate of change of total electron content index as the irregularity parameter based on the global positioning system data. The background electron density and plasma irregularities are closely controlled by the Earth's magnetic field, with averaged enhancements close to the magnetic poles. The climatological maps in magnetic latitude/magnetic local time coordinates show predominant plasma irregularities near the dayside cusp, polar cap, and nightside auroral oval. These irregularities may be associated with large‐scale plasma structures such as polar cap patches, auroral blobs, auroral particle precipitation, and the equatorward wall of the ionospheric trough. The spatial distributions of irregularities depend on the interplanetary magnetic field (IMF). By filtering the irregularity parameters according to IMF By, we find a clear asymmetry of the spatial distribution in the cusp and polar cap between the Northern (NH) and Southern Hemispheres (SH). For negative IMF By, irregularities are stronger in the dusk (dawn) sector in the NH (SH) and vice versa. This feature is in agreement with the high‐latitude ionospheric convection pattern that is regulated by the IMF By component. The plasma irregularities are also controlled by the solar activity within the current declining solar cycle. The irregularities in the SH polar cap show a seasonal variation with higher values from September to April, while the seasonal variation in the NH is only obvious around solar maximum during 2014–2015.

• Jin, Yaqi; Moen, Jøran Idar; Spicher, Andres; Oksavik, Kjellmar; Miloch, Wojciech Jacek & Clausen, Lasse Boy Novock [Show all 8 contributors for this article] (2019). Simultaneous rocket and scintillation observations of plasma irregularities associated with a reversed flow event in the cusp ionosphere. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 124(8), p. 7098–7111. doi: 10.1029/2019JA026942. Full text in Research Archive Show summary

  We present an overview of the ionospheric conditions during the launch of the Investigation of Cusp Irregularities 3 (ICI‐3) sounding rocket. ICI‐3 was launched from Ny‐Ålesund, Svalbard, at 7:21.31 UT on 3 December 2011. The objective of ICI‐3 was to intersect the reversed flow event (RFE), which is thought to be an important source for the rapid development of ionospheric irregularities in the cusp ionosphere. The interplanetary magnetic field was characterized by strongly negative Bz and weakly negative By. The EISCAT Svalbard radar (ESR) 32‐m beam was operating in a fast azimuth sweep mode between 180° (south) and 300° (northwest) at an elevation angle of 30°. The ESR observed a series of RFEs as westward flow channels that were opposed to the large‐scale eastward plasma flow in the prenoon sector. ICI‐3 intersected the first RFE in the ESR field of view and observed flow structures that were consistent with the ESR observations. Furthermore, ICI‐3 revealed finer‐scale flow structures inside the RFE. The high‐resolution electron density data show intense fluctuations at all scales throughout the RFE. The ionospheric pierce point of the GPS satellite PRN30, which was tracked at Hornsund, intersected the RFE at the same time. The GPS scintillation data show moderate phase scintillations and weak amplitude scintillations. A comparison of the power spectra reveals a good match between the ground‐based GPS carrier phase measurements and the spectral slope of the in situ electron density data in the lower frequency range. It demonstrates the possibility of modelling GPS scintillations from high‐resolution in situ electron density data.

• Jin, Yaqi; Miloch, Wojciech Jacek; Moen, Jøran Idar & Clausen, Lasse Boy Novock (2018). Solar cycle and seasonal variations of the GPS phase scintillation at high latitudes. Journal of Space Weather and Space Climate. 8. doi: 10.1051/swsc/2018034. Full text in Research Archive Show summary

  We present the long-term statistics of the GPS phase scintillation in the polar region (70°–82° magnetic latitude) by using the GPS scintillation data from Ny-Ålesund for the period 2010–2017. Ny-Ålesund is ideally located to observe GPS scintillations modulated by the ionosphere cusp dynamics. The results show clear solar cycle and seasonal variations, with the GPS scintillation occurrence rate being much higher during solar maximum than during solar minimum. The seasonal variations show that scintillation occurrence rate is low during summer and high during winter. The highest scintillation occurrence rate is around magnetic noon except for December 2014 (solar maximum) when the nightside scintillation occurrence rate exceeds the dayside one. In summer, the dayside scintillation region is weak and there is a lack of scintillations in the nightside polar cap. The most intriguing features of the seasonal variations are local minima in the scintillation occurrence rate around winter solstices. They correspond to local minima in the F2 peak electron density. The dayside scintillation region migrates equatorward from summer to winter and retreats poleward from winter to summer repetitively in a magnetic latitude range of 74°–80°. This latitudinal movement is likely due to the motion of the cusp location due to the tilt of the Earth’s magnetic field and the impact of the sunlight.

• Paulsson, Joakim John Paul; Spicher, Andres; Clausen, Lasse Boy Novock; Moen, Jøran Idar & Miloch, Wojciech Jacek (2018). Wake Potential and Wake Effects on the Ionospheric Plasma Density Measurements With Sounding Rockets. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 123(11), p. 9711–9725. doi: 10.1029/2017JA025004. Full text in Research Archive Show summary

  A new method is developed to systematically study variations in the electrostatic potential around a spinning spacecraft in flowing plasma. We argue that the main modulation of this potential is due to wake leading to different depletions in electron and ion densities. This wake potential can be calculated with the help of electric currents measured by Langmuir probes mounted on a boom system and the assumption of Boltzmann‐distributed electrons. The wake position is determined with the electric field measurements. We apply this method to data from the Investigation of Cusp Irregularities 3 ionospheric sounding rocket and find the observed wake to be larger than expected from the flow velocity and the Mach cone formation, which can be explained by the presence of booms. By using the wake potential to filter the rocket data, we show that this method is robust during highly dynamic plasma conditions and that it can be used to improve the quality of plasma density measurements and reduce the wake effects.

• Clausen, Lasse Boy Novock & Nickisch, Hannes (2018). Automatic Classification of Auroral Images From the Oslo Auroral THEMIS (OATH) Data Set Using Machine Learning. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 123(7), p. 5640–5647. doi: 10.1029/2018JA025274. Full text in Research Archive Show summary

  Based on their salient features we manually label 5,824 images from various Time History of Events and Macroscale Interactions during Substorms (THEMIS) all‐sky imagers; the labels we use are clear/no aurora, cloudy, moon, arc, diffuse, and discrete. We then use a pretrained deep neural network to automatically extract a 1,001‐dimensional feature vector from these images. Together, the labels and feature vectors are used to train a ridge classifier that is then able to correctly predict the category of unseen auroral images based on extracted features with 82% accuracy. If we only distinguish between a binary classification aurora and no aurora, the true positive rate increases to 96%. While this study paves the way for easy automatic classification of all auroral images from the THEMIS all‐sky imager chain, we believe that the methodology shown here is readily applied to all images from any other auroral imager as long as the data are available in digital form. Both the neural network and the ridge classifier are free, off‐the‐shelf computer codes; the simplicity of our approach is demonstrated by the fact that our entire analysis comprises about 50 lines of Python code. Automatically attaching labels to all available all‐sky imager data would enable statistical studies of unprecedented scope.

• D'Angelo, Giulia; Piersanti, Mirko; Alfonsi, Lucilla; Spogli, Luca; Clausen, Lasse Boy Novock & Coco, Igino [Show all 8 contributors for this article] (2018). The response of high latitude ionosphere to the 2015 St. Patrick's day storm from in situ and ground based observations. Advances in Space Research. ISSN 0273-1177. 62(3), p. 638–650. doi: 10.1016/j.asr.2018.05.005. Full text in Research Archive Show summary

  The storm onset of the so-called “St. Patrick’s day geomagnetic storm”, on March 17th, 2015 triggered several fluctuations of the electron density in the ionosphere causing severe scintillations at high latitudes of both hemispheres. Leveraging on ground-based Global Navigation Satellite Systems (GNSS) receivers we investigate the ionospheric response to the main phase of the most intense storm of the current solar cycle, in terms of phase scintillations on L-band signals recorded simultaneously in Antarctica and in the Arctic. In detail, we analyse phase scintillation index (σϕ) data from Eureka (79.99°N, 274.10°E), Concordia (75.10°S, 123.35°E), Resolute Bay (74.75°N, 265.00°E), Mario Zucchelli (74.41°S, 164.10°E), Ny-Ålesund (78.92°N, 11.98°E) and Zhongshan (69.37°S, 76.37°E) stations. Furthermore, by using ancillary data obtained from in-situ and ground-based observations, we investigate the origin and the evolution of the ionospheric irregularities causing scintillations, reconstructing the ionospheric background in which such irregularities formed and moved. The multi-instrumental approach used in this work allows identifying the Antarctic ionosphere as the most responsive to the solar perturbation driving the storm. Our study reveals how the in-situ electron density data can be used to reconstruct the picture of the ionospheric dynamics, both locally and globally. Finally, our results identify the important role played by particles precipitation in triggering the observed scintillations.

• Miloch, Wojciech Jacek; Jin, Yaqi; Xiong, Chao; Kervalishvili, Guram; Spicher, Andres & Clausen, Lasse Boy Novock [Show all 7 contributors for this article] (2018). Ionospheric plasma irregularities studied with Swarm satellites. E3S Web of Conferences. 62, p. 1–6. doi: 10.1051/e3sconf/20186201009. Full text in Research Archive Show summary

  To study and characterise the ionospheric plasma irregularities at all latitudes, one can employ in-situ measurements by satellites in polar orbits, such as the European Space Agency’s Swarm mission. Based on the Swarm data, we have developed the Ionospheric Plasma IRregularities (IPIR) product for a global characterisation of ionospheric irregularities along the satellite track at all latitudes. This new Level-2 data product combines complementary datasets from the Swarm satellites: the electron density from the electric field instrument, the GPS data from the onboard GPS receiver, and the magnetic field data from the onboard magnetometers. This can be used as a new tool for global studies of ionospheric irregularities and turbulence.

• Chernyshov, Aleksander A.; Spicher, Andres; Ilyasov, Askar A.; Miloch, Wojciech Jacek; Clausen, Lasse Boy Novock & Saito, Yoshifumi [Show all 8 contributors for this article] (2018). Studies of small-scale plasma inhomogeneities in the cusp ionosphere using sounding rocket data. Physics of Plasmas. ISSN 1070-664X. 25(4). doi: 10.1063/1.5026281. Full text in Research Archive Show summary

  Microprocesses associated with plasma inhomogeneities are studied on the basis of data from the Investigation of Cusp Irregularities (ICI-3) sounding rocket. The ICI-3 rocket is devoted to investigating a reverse flow event in the cusp F region ionosphere. By numerical stability analysis, it is demonstrated that inhomogeneous-energy-density-driven (IEDD) instability can be a mechanism for the excitation of small-scale plasma inhomogeneities. The Local Intermittency Measure (LIM) method also applied the rocket data to analyze irregular structures of the electric field during rocket flight in the cusp. A qualitative agreement between high values of the growth rates of the IEDD instability and the regions with enhanced LIM is observed. This suggests that IEDD instability is connected to turbulent non-Gaussian processes.

• Hoang, Huy Minh; Clausen, Lasse Boy Novock; Røed, Ketil; Bekkeng, Tore Andre; Trondsen, Espen & Lybekk, Bjørn [Show all 11 contributors for this article] (2018). The Multi-Needle Langmuir Probe System on Board NorSat-1. Space Science Reviews. ISSN 0038-6308. 214(4). doi: 10.1007/s11214-018-0509-2. Full text in Research Archive Show summary

  On July 14th, 2017, the first Norwegian scientific satellite NorSat-1 was launched into a high-inclination (98∘), low-Earth orbit (600 km altitude) from Baikonur, Kazakhstan. As part of the payload package, NorSat-1 carries the multi-needle Langmuir probe (m-NLP) instrument which is capable of sampling the electron density at a rate up to 1 kHz, thus offering an unprecedented opportunity to continuously resolve ionospheric plasma density structures down to a few meters. Over the coming years, NorSat-1 will cross the equatorial and polar regions twice every 90 minutes, providing a wealth of data that will help to better understand the mechanisms that dissipate energy input from larger spatial scales by creating small-scale plasma density structures within the ionosphere. In this paper we describe the m-NLP system on board NorSat-1 and present some first results from the instrument commissioning phase. We show that the m-NLP instrument performs as expected and highlight its unique capabilities at resolving small-scale ionospheric plasma density structures.

• Hoang, Huy Minh; Røed, Ketil; Bekkeng, Tore Andre; Moen, Jøran Idar; Spicher, Andres & Clausen, Lasse Boy Novock [Show all 9 contributors for this article] (2018). A study of data analysis techniques for the multi-needle Langmuir probe. Measurement Science and Technology. ISSN 0957-0233. 29(6). doi: 10.1088/1361-6501/aab948. Full text in Research Archive

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• Mann, Ingrid; Olsen, Sveinung viggo; Eilertsen, Yngve; Yokoyama, Yoshihiro; Tinguely, Jean-Claude & Spicher, Andres [Show all 20 contributors for this article] (2026). Maxidusty-2: The SCIENCE AND CAMPAIGN OVERVIEW. Full text in Research Archive
• Mann, Ingrid; Olsen, Sveinung viggo; Eilertsen, Yngve; Yokoyama, Yoshihiro; Tinguely, Jean-Claude & Spicher, Andres [Show all 18 contributors for this article] (2026). Dust and ionospheric constituents measured in the MLT during noctilucent cloud conditions. Full text in Research Archive
• Mann, Ingrid; Olsen, Sveinung viggo; Eilertsen, Yngve; Yokoyama, Yoshihiro; Tinguely, Jean-Claude & Spicher, Andres [Show all 18 contributors for this article] (2026). MXD2 Science and Campaign Overview. Full text in Research Archive
• Mann, Ingrid; Olsen, Sveinung viggo; Eilertsen, Yngve; Yokoyama, Yoshihiro; Tinguely, Jean-Claude & Spicher, Andres [Show all 15 contributors for this article] (2026). Maxidusty-2 in-situ measurements and sample collection in NLC/PMSE layers. Full text in Research Archive
• Holdcroft, Sam; Bocci, Alessio; Scholtz, Laura-Kristin; Retselis, Anastasios-Faidon; Knutsen, Elise Wright & Jebali, Ramsey Al [Show all 20 contributors for this article] (2025). CENSSAT-1 mission concept: a CubeSat for space weather monitoring. doi: 10.5281/ZENODO.17036544. Full text in Research Archive Show summary

  This paper presents an introduction to the CENSSAT-1 mission, an 8U CubeSat, which aims to study space situational awareness. It will investigate the effects of space weather on Earth from a 500 km orbit, using a camera, multi-purpose particle detector, and a Langmuir probe. It will additionally monitor space debris using a radar instrument, and conduct experiments on optimal control and drag based manoeuvring. CENSSAT-1 is aiming for launch in 2027.

• 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; 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
• 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
• 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
• 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
• 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
• Huyghebaert, Devin Ray; Mann, Ingrid; Baddeley, Lisa; Johnsen, Magnar Gullikstad; Clausen, Lasse & Gausa, Michael [Show all 9 contributors for this article] (2022). EISCAT 3D Norway - An Overview. Full text in Research Archive
• 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
• 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
• Miloch, Wojciech Jacek; Usui, Hideyuki; Miyake, Yohei; Mortensen, Mikael; Chernyshov, A.A. & Baddeley, Lisa [Show all 11 contributors for this article] (2021). Long-term and sustainable research- based student mobility projects within space weather. Full text in Research Archive
• Spicher, Andres; LaBelle, James William; Bonnell, John W; Bounds, Scott; Clausen, Lasse Boy Novock & Mare, Francesca Di [Show all 16 contributors for this article] (2020). On multi-scale density irregularities observed by sounding rockets within regions of enhanced scintillations in the cusp ionosphere. Full text in Research Archive
• Mare, Francesca Di; Spicher, Andres; Clausen, Lasse Boy Novock; Miloch, Wojciech Jacek & Moen, Jøran Idar (2020). Turbulent Signatures in the Polar Cusp Ionosphere using sounding rocket mission observations. Full text in Research Archive
• Mare, Francesca Di; Spicher, Andres; Clausen, Lasse Boy Novock; Miloch, Wojciech Jacek & Moen, Jøran Idar (2020). Turbulence Signatures in the Polar/Cusp Ionosphere based on ICI sounding rocket missions. Full text in Research Archive
• Miloch, Wojciech Jacek; Alfonsi, Lucilla; Spogli, Luca; Wood, Alan; Sahtahmassebi, Golnaz & Clausen, Lasse [Show all 10 contributors for this article] (2020). Variability of Ionospheric Plasma Based on Swarm Satellite Data. Full text in Research Archive
• Miloch, Wojciech Jacek; Jin, Yaqi; Xiong, Chao; Brask, Steffen Mattias; Kotova, Daria & Kervalishvili, Guram [Show all 9 contributors for this article] (2020). Ionospheric Plasma IRregularities (IPIR data products). Full text in Research Archive
• Spicher, Andres; Moen, Jøran Idar; Clausen, Lasse Boy Novock & Miloch, Wojciech Jacek (2019). On the source and nature of ionospheric plasma irregularities: advances made through the Investigation of Cusp irregularities sounding rocket program. Full text in Research Archive
• Spicher, Andres; Oksavik, Kjellmar; Jin, Yaqi; Clausen, Lasse Boy Novock; Zettergren, Matthew D. & Deshpande, K. B. [Show all 8 contributors for this article] (2019). A reverse flow event as the onset of ionospheric scintillation irregularities in the cusp. Full text in Research Archive
• Spicher, Andres; Oksavik, Kjellmar; Jin, Yaqi; Moen, Jøran Idar; Baddeley, Lisa & Clausen, Lasse Boy Novock (2019). On the sources of Cusp Ionospheric Scintillation Irregularities. Full text in Research Archive
• Spicher, Andres; Deshpande, Kshitija; Zettergren, Matthew D.; Oksavik, Kjellmar; Jin, Yaqi & Clausen, Lasse Boy Novock [Show all 7 contributors for this article] (2019). Modeling scintillation produced by ionospheric Kelvin Helmholtz in the cusp ionosphere using GEMINI-SIGMA. Full text in Research Archive Show summary

  Ionospheric irregularities are known to cause fluctuations in radio signals called scintillation in the phase and amplitude of the complex signal. The turbulent structures responsible for the scintillation are a few hundreds of meters to few tens of kilometers scale sizes (intermediate scale sizes). With the growing interest in high latitude scintillation, we would like to investigate the effect of typical physical mechanisms on the radio scintillation. Here we present our modeling studies of Global Positioning System (GPS) scintillation through Kelvin Helmholtz instability (KHI) in the cusp region. For modeling we use the first principles based Geospace Environment Model of Ion-Neutral Interactions (GEMINI) and Satellite-beacon Ionospheric-scintillation Global Model of the upper Atmosphere (SIGMA). We utilize a cusp event study with detailed observations from the EISCAT Svalbard Radar (ESR) and scintillations detected from a network of four Global Navigation Satellite Systems (GNSS) receivers in Svalbard. The event presents evidences of the role of magnetosphere-ionosphere coupling in the generation of plasma irregularities and scintillations in the cusp. Using numerical simulations, we investigate the potential role of the Kelvin-Helmholtz instability in producing such scintillation. Furthermore, we compare the results with characteristics of GPS scintillations associated with a polar cap patch and the gradient drift instability to deduce distinctive characteristics of the respective plasma irregularities.

• Miloch, Wojciech Jacek; Kotova, Daria; Jin, Yaqi; Xiong, Chao; Brask, Steffen & Kervalishvili, Guram [Show all 9 contributors for this article] (2019). Ionospheric plasma irregularities studied globally with the Swarm satellites. Full text in Research Archive
• Mare, Francesca Di; Spicher, Andres; Clausen, Lasse Boy Novock & Moen, Jøran Idar (2019). Turbulence observations in the Polar/Cusp Ionosphere using ICI data missions. Full text in Research Archive
• Mare, Francesca Di; Spicher, Andres; Clausen, Lasse Boy Novock & Moen, Jøran Idar (2019). Turbulence observations in the Polar/Cusp Ionosphere using ICI sounding rocket data. Full text in Research Archive
• Mare, Francesca Di; Spicher, Andres; Clausen, Lasse Boy Novock & Moen, Jøran Idar (2019). Mapping of turbulence at the high-latitude Ionosphere using ICI-2 and ICI-3 sounding rocket data. Full text in Research Archive
• Moen, Jøran Idar; Oksavik, Kjellmar; Carlson, Herbert C; Spicher, Andres; Bekkeng, Tore Andre & Clausen, Lasse Boy Novock [Show all 12 contributors for this article] (2018). The Investigation of Cusp Irregularities Rocket Program. Full text in Research Archive
• Moen, Jøran Idar; Hoang, Huy Minh; Clausen, Lasse Boy Novock & Trondsen, Espen (2018). The multi-Needle Langmuir probe system for exploration of the global ionosphere. Full text in Research Archive
• Spicher, Andres; Clausen, Lasse Boy Novock; Miloch, Wojciech Jacek; Jin, Yaqi; Lofstad, Victoria Emilie & Moen, Jøran Idar (2018). Polar cap patch climatology based on Swarm density data. Full text in Research Archive
• Spicher, Andres; Moen, Jøran Idar; Clausen, Lasse Boy Novock; Miloch, Wojciech Jacek & Blix, Kolbjørn (2018). 4DSpace long term plans towards a multi-satellite M-Class mission. Full text in Research Archive
• Jin, Yaqi; Miloch, Wojciech Jacek; Clausen, Lasse Boy Novock; Spicher, Andres; Stolle, Claudia & Kervalishvili, G. [Show all 7 contributors for this article] (2018). Ionospheric Plasma Irregularities Characterized by the Swarm satellites. Full text in Research Archive
• Jin, Yaqi; Spicher, Andres; Xiong, Chao; Clausen, Lasse Boy Novock; Stolle, Claudia & Kervalishvili, G. [Show all 7 contributors for this article] (2018). Detecting high-latitude ionospheric plasma irregularities by Swarm satellites. Full text in Research Archive
• 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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