Yaqi Jin

• Ivarsen, Magnus Fagernes; St-Maurice, Jean Pierre; Hussey, Glenn C.; McWilliams, Kathryn; Jin, Yaqi & Huyghebaert, Devin Ray [Vis alle 8 forfattere av denne artikkelen] (2025). Eastward transients in the dayside ionosphere. II. A parallel-plate capacitorlike effect. Physical Review E (PRE). ISSN 2470-0045. 112(4). doi: 10.1103/3bzj-bsf8. Fulltekst i vitenarkiv
• Ivarsen, Magnus Fagernes; St-Maurice, Jean Pierre; Hussey, Glenn C.; Billet, Daniel; Huyghebaert, Devin Ray & Jin, Yaqi [Vis alle 17 forfattere av denne artikkelen] (2025). Eastward transients in the dayside ionosphere. I. Electrodynamics on closed field lines. Physical Review E (PRE). ISSN 2470-0045. 112(4). doi: 10.1103/r6bv-pzlq. Fulltekst i vitenarkiv Vis sammendrag

  At night in Earth's polar regions, energetic aurorae frequently penetrate into the atmosphere, with the peculiar effect of driving turbulent electrojet currents in the bottomside ionosphere. During the day, however, Earth's plasma environment becomes highly conductive, owing to the constant flux of extreme ultraviolet radiation emitted from the Sun. The high-conductivity plasma in the dayside ionosphere can effectively short out plasma turbulence around aurorae, and so electrojet turbulence is thought rare in the dayside high-latitude ionosphere. In this paper we show observations to the contrary. During the onset of the 23 April 2023 geomagnetic storm, we observed prolific small-scale plasma turbulence in the dayside 𝐸 region on closed magnetic field lines just equatorward of the cusp. Using data from two orbiting satellites, we infer the locations of the cusp and the distributed presence of diffuse aurorae, through observations of electron fluxes and wave-particle interactions near the magnetospheric equator, on nearby magnetic field lines. The resulting diffuse aurorae pass electric fields and produce unstable gradients in the plasma density. The number and intensity of the falling charges momentarily overwhelm the capacity of the lower ionosphere to extinguish the strong electric fields that follow from this action, spurring the growth of transient, turbulent electrojets, or Hall currents. In the 23 April 2023 case study, we establish a correlation between observations of chorus-wave activity near the magnetospheric equator and observations of turbulent electrojets in the ionosphere on closed magnetic field lines, from which we infer a causal chain where magnetospheric plasma waves ultimately drive small-scale turbulence in the ionosphere. We show how the predictions are brought to fruition in similar supporting events. Finally, we briefly discuss the implications that this discovery bears for the electrodynamics of the dayside ionosphere. In the following paper [M. F. Ivarsen, Phys. Rev. E 112, 045203 (2025)] we follow the lengthy argument to a logical conclusion, leading to an alternative description of electrodynamics in the cusp region.

• 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. Fulltekst i vitenarkiv Vis sammendrag

  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

• Kotova, Daria; Sinevich, A.A.; Chernyshov, A.A.; Chugunin, D.V.; Jin, Yaqi & Miloch, Wojciech Jacek (2025). Strong turbulent flow in the subauroral region in the Antarctic can deteriorate satellite-based navigation signals. Scientific Reports. 15(1), s. 3458–3458. doi: 10.1038/s41598-025-86960-6. Fulltekst i vitenarkiv
• Buschmann, Lisa Marie; Asamura, K.; Clausen, Lasse; Jin, Yaqi; Kojima, H. & Kumamoto, A. [Vis alle 13 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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 [Vis alle 20 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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).

• 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. Fulltekst i vitenarkiv Vis sammendrag

  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 [Vis alle 20 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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).

• Miloch, Wojciech Jacek; Kotova, Daria & Jin, Yaqi (2024). Ionospheric plasma irregularities over Dronning Maud Land in Antarctica and associated space weather effects. Fundamental Plasma Physics. 12. doi: 10.1016/j.fpp.2024.100076. Fulltekst i vitenarkiv Vis sammendrag

  Ionospheric plasma irregularities and associated space weather effects over Dronning Maud Land in Antarctica are studied with a multi-instrument approach. It is demonstrated during a substorm event that auroral particle precipitation associated with the edges of auroral arcs can lead to irregularities in the ionospheric plasma density that can have significant impact on trans-ionospheric radio waves. Both refractive and diffractive effects are observed on signals from the GNSS satellites, where the latter are identified by the ionospheric free linear combination approach and amplitude scintillation. Thus, intense auroral particle precipitation can lead to plasma irregularities at scales from several kilometers down to and below the Fresnel radius, and they can result in space weather effects which can lead to losing the integrity of the GNSS signals.

• Zhang, Kedeng; Wang, Hui; Xia, Hao; Wang, Wenbin; Liu, Jing & Zhang, Shunrong [Vis alle 7 forfattere av denne artikkelen] (2024). The Turkey Earthquake Induced Equatorial Ionospheric Current Disturbances on 6 February 2023. Remote Sensing. 16(2). doi: 10.3390/rs16020272. Fulltekst i vitenarkiv Vis sammendrag

  An earthquake is a seismic event resulting from a sudden release of energy in the lithosphere, which produces waves that can propagate through the atmosphere into the ionosphere, causing ionospheric disturbances, and excites an additional electric field in the lower ionosphere. Two large-scale traveling ionospheric disturbances (LSTIDs) at daytime Turkey longitudes were found, with phase speeds of 534 and 305 m/s, respectively, after the second strong earthquake at 10:24 UT on 6 February 2023. During strong earthquakes, the equatorial ionospheric currents including the E-region equatorial electrojet (EEJ) and F-region ionospheric radial current (IRC) might be perturbed. At the Tatuoca station in Brazil, we observed a stronger-than-usual horizontal magnetic field associated with the EEJ, with a magnitude of ~100 nT. EEJ perturbations are mainly controlled by neutral winds, especially zonal winds. In the equatorial F-region, a wave perturbation of the IRC was caused by a balance of the electric field generated by the zonal winds at ~15° MLat, the F-region local winds driven by atmospheric resonance, and the additional polarization electric field. Our findings better the understanding of the complex interplay between seismic events and ionospheric current disturbances.

• Enengl, Florine; Spogli, L.; Kotova, Daria; Jin, Yaqi; Oksavik, Kjellmar & Partamies, Noora [Vis alle 7 forfattere av denne artikkelen] (2024). Investigation of Ionospheric Small-Scale Plasma Structures Associated With Particle Precipitation. Space Weather. 22(1). doi: 10.1029/2023SW003605. Fulltekst i vitenarkiv Vis sammendrag

  We investigate the role of auroral particle precipitation in small-scale (below hundreds of meters) plasma structuring in the auroral ionosphere over the Arctic. In this scope, we analyze together data recorded by an Ionospheric Scintillation Monitor Receiver (ISMR) of Global Navigation Satellite System (GNSS) signals and by an All-Sky Imager located in Longyearbyen, Svalbard (Norway). We leverage on the raw GNSS samples provided at 50 Hz by the ISMR to evaluate amplitude and phase scintillation indices at 1 s time resolution and the Ionosphere-Free Linear Combination at 20 ms time resolution. The simultaneous use of the 1 s GNSS-based scintillation indices allows identifying the scale size of the irregularities involved in plasma structuring in the range of small (up to few hundreds of meters) and medium-scale size ranges (up to few kilometers) for GNSS frequencies and observational geometry. Additionally, they allow identifying the diffractive and refractive nature of fluctuations on the recorded GNSS signals. Six strong auroral events and their effects on plasma structuring are studied. Plasma structuring down to scales of hundreds of meters is seen when strong gradients in auroral emissions at 557.7 nm cross the line of sight between the GNSS satellite and receiver. Local magnetic field measurements confirm small-scale structuring processes coinciding with intensification of ionospheric currents. Since 557.7 nm emissions primarily originate from the ionospheric E-region, plasma instabilities from particle precipitation at E-region altitudes are considered to be responsible for the signatures of small-scale plasma structuring highlighted in the GNSS scintillation data.

• Ivarsen, Magnus Fagernes; St-Maurice, J.-P.; Park, J.; Klenzing, J.; Jin, Yaqi & Lee, W. (2024). Plasma Structure Decay Rates in the Equatorial Ionosphere Are Strongly Coupled by Turbulence. Geophysical Research Letters. ISSN 0094-8276. 51(18). doi: 10.1029/2024GL109441. Fulltekst i vitenarkiv Vis sammendrag

  Equatorial plasma irregularities in the ionospheric F-region proliferate after sunset, causing the most apparent radio scintillation “hot-spot” in geospace. These irregularities are caused by plasma instabilities, and appear mostly in the form of under-densities that rise up from the F-region's bottomside. After an irregularity production peak at sunset, the amplitude of the resulting turbulence decays with time. Analyzing a large database of irregularity spectra observed by one of the European Space Agency's Swarm satellites, we have applied a novel but conceptually simple statistical analysis to the data, finding that turbulence in the F-region tends to decay with a uniform, scale-independent rate, thereby confirming and extending the results from an earlier case study. We find evidence for two regimes, one valid post-sunset (1.4 hr decay rate) and one valid post-midnight (2.6 hr). Our results should be of utility for large-scale space weather modeling efforts that are unable to resolve turbulent effects.

• 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. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Ivarsen, Magnus Fagernes; Jin, Yaqi; Spicher, Andres; St-Maurice, Jean-Pierre; Park, Jaeheung & Billett, Daniel (2023). GNSS Scintillations in the Cusp, and the Role of Precipitating Particle Energy Fluxes. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 128(10). doi: 10.1029/2023JA031849. Fulltekst i vitenarkiv Vis sammendrag

  Using a large data set of ground-based GNSS scintillation observations coupled with in situ particle detector data, we perform a statistical analysis of both the input energy flux from precipitating particles, and the observed occurrence of density irregularities in the northern hemisphere cusp. By examining trends in the two data sets relating to geomagnetic activity, we conclude that observations of irregularities in the cusp grows increasingly likely during storm-time, whereas the precipitating particle energy flux does not. We thus find a weak or nonexistent statistical link between geomagnetic activity and precipitating particle energy flux in the cusp. This is a result of a previously documented tendency for the cusp energy flux to maximize during northward IMF, when density irregularities tend not to be widespread, as we demonstrate. At any rate, even though ionization and subsequent density gradients directly caused by soft electron precipitation in the cusp are not to be ignored for the trigger of irregularities, our results point to the need to scrutinize additional physical processes for the creation of irregularities causing scintillations in and around the cusp. While numerous phenomena known to cause density irregularities have been identified and described, there is a need for a systematic evaluation of the conditions under which the various destabilizing mechanisms become important and how they sculpt the observed ionospheric “irregularity landscape.” As such, we call for a quantitative assessment of the role of particle precipitation in the cusp, given that other factors contribute to the production of irregularities in a major way.

• Zhang, Kedeng; Song, Huimin; Wang, Hui; Liu, Jing; Wang, Wenbin & Wan, Xin [Vis alle 8 forfattere av denne artikkelen] (2023). Dynamics of the Tongue of Ionizations During the Geomagnetic Storm on 7 September 2015: The Altitudinal Dependences. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 128(11). doi: 10.1029/2023JA031735. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Using the electron density (Ne) observations from the Defense Meteorological Satellite Program, and Constellation Observing Systems for Meteorology, Ionosphere, and Climate mission and simulations from the Thermosphere Ionosphere Electrodynamic General Circulation Model. we investigate the dynamic evolution of the polar tongue of ionization (TOI) from double to single structures at different altitudes during a geomagnetic storm. The modeled Ne depicted that double and single TOIs occurred at altitudes above 300 km, respectively. During the northward turning of interplanetary magnetic field (IMF) Bz, the afternoon TOI disappeared and the morning TOI was reduced. The plasma transport due to neutral winds and ambipolar diffusion facilitated (prevented) the depletion of plasma density of the morning TOI at 300 (500) km, with a relative contribution of 42.8% and 28.6% (−15.4% and −76.9%), respectively. Downward E × B drifts led to an enhancement/reduction of plasma density in the storm enhanced density region in the lower/upper ionosphere. During the duskward turning of IMF By, the morning TOI could be mostly attributed to the anti‐sunward plasma drifts (75.8% at 300 km, 100% at 500 km), with a relatively stronger role of the zonal component than that of meridional E × B drifts. The upward E × B drifts were important/ignorable in the upper/lower ionosphere. Both the neutral winds and ambipolar diffusion resulted in an accumulation of plasma density of the morning TOI at 300 km indirectly (24.2%), however, their roles were minor at 500 km.

• 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. Fulltekst i vitenarkiv
• Jin, Yaqi; Miloch, Wojciech Jacek; Kotova, Daria; Jacobsen, Knut Stanley; Stevanović, Đorđe & Clausen, Lasse [Vis alle 8 forfattere av denne artikkelen] (2023). Modeling TEC Irregularities in the Arctic Ionosphere Using Empirical Orthogonal Function Method. Space Weather. 21(8). doi: 10.1029/2023SW003531. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Song, Hosub; Park, Jaeheung; Jin, Yaqi; Otsuka, Yuichi; Buchert, Stephan & Lee, Jaejin [Vis alle 7 forfattere av denne artikkelen] (2023). Tandem Observations of Nighttime Mid-Latitude Topside Ionospheric Perturbations. Space Weather. 21(2). doi: 10.1029/2022SW003312. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Nighttime medium‐scale traveling ionospheric disturbances (MSTIDs) have been generally observed by ground‐based instruments. However, they provide 2‐dimensional images over only a limited field of view and are not distributed globally. The ground‐based observations reported that MSTID wavefronts exhibit backward‐C shapes virtually straddling the dip equator. In situ plasma density measurements onboard individual satellites could overcome the limited coverage of ground‐based MSTID observations. But, most of those spacecrafts could obtain only 1‐dimensional profiles of plasma density, which leaves uncertain whether the observed perturbations generally have the characteristic directivity of MSTIDs. This paper addresses this knowledge gap by statistically investigating nighttime perturbations in the mid‐latitude topside ionosphere observed by tandem satellites, Swarm A and C. We cross‐correlate the plasma density profiles observed by Swarm A and C. The correlation coefficient tends to increase as the two spacecraft move closer, allowing us to derive the disturbances' directivity whenever the Swarm A and C observations are correlated significantly. The directivity statistics agree well with the backward‐C shape. Furthermore, the wavefront directions have clear dependence on magnetic latitudes while they are not as well aligned with local time, which is also consistent with previous reports on nighttime MSTIDs using ground‐based observations and computer simulations. Additionally, we demonstrate that the nighttime MSTIDs can increase the topside Rate Of Total electron content Index above Swarm. All the above‐mentioned results support that the nighttime mid‐latitude perturbations observed by Swarm can be identified as MSTIDs on the whole, which is the most important finding of this paper.

• Ivarsen, Magnus Fagernes; St‐Maurice, Jean-Pierre; Hussey, Glenn C.; Spicher, Andres; Jin, Yaqi & Lozinsky, Adam [Vis alle 10 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Yu, Tingting; Cai, Xuguang; Ren, Zhipeng; Wang, Zihan; Pedatella, Nicholas. M. & Jin, Yaqi (2023). Investigation of Interhemispheric Asymmetry of the Thermospheric Composition Observed by GOLD During the First Strong Geomagnetic Storm in Solar-Cycle 25, 1: IMF B<inf>y</inf> Effects. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 128(10). doi: 10.1029/2023JA031429. Fulltekst i vitenarkiv Vis sammendrag

  Abstract An interhemispheric asymmetry of thermospheric Oxygen (O) to Nitrogen (N 2 ) column density ratio (∑O/N 2 ) variations was observed by the Global‐scale Observations of the Limb and Disk (GOLD) during the 3–5 November 2021 geomagnetic storm. ∑O/N 2 depletion is more equatorward in the local morning than in the local afternoon in the northern hemisphere (NH), while more equatorward in the local afternoon than the local morning in the southern hemisphere (SH). The Thermosphere Ionosphere Electrodynamics General Circulation Model simulations reproduced the observed ∑O/N 2 asymmetry. The impacts of interplanetary magnetic field (IMF) east‐west component ( B y ) on the interhemispheric asymmetry of ∑O/N 2 depletion was investigated. Comparisons of simulation results with and without real B y show that the dominant positive IMF B y results in the Joule heating maximum occurring in the local afternoon of NH and local morning in the SH during the storm initial phase, which generates the corresponding ∑O/N 2 changes. Additionally, the IMF B y during this storm are more crucial in the SH than in the NH. Without B y , equatorward penetration of the ∑O/N 2 depletion in GOLD Field of View are almost same in the SH. However, in the NH, there is still more equatorward depletion in the local morning than the local afternoon without B y .

• Spicher, Andres; LaBelle, James; Bonnell, John W.; Roglans, Roger; Moser, Chrystal & Fuselier, Stephen A. [Vis alle 18 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Jin, Yaqi; Clausen, Lasse; Miloch, Wojciech Jacek; Høeg, Per; Jarmołowski, Wojciech & Wielgosz, Pawel [Vis alle 13 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  This paper addresses the long-term climatology (over two solar cycles) of total electron content (TEC) irregularities from a polar cap station (Thule) using the rate of change of the TEC index (ROTI). The climatology reveals variabilities over different time scales, i.e., solar cycle, seasonal, and diurnal variations. These variations in different time scales can be explained by different drivers/contributors. The solar activity (represented by the solar radiation index F10.7P) dominates the longest time scale variations. The seasonal variations are controlled by the interplay of the energy input into the polar cap ionosphere and the solar illumination that damps the amplitude of ionospheric irregularities. The diurnal variations (with respect to local time) are controlled by the relative location of the station with respect to the auroral oval. We further decompose the climatology of ionospheric irregularities using the empirical orthogonal function (EOF) method. The first four EOFs could reflect the majority (99.49%) of the total data variability. A climatological model of ionospheric irregularities is developed by fitting the EOF coefficients using three geophysical proxies (namely, F10.7P, Bt, and Dst). The data-model comparison shows satisfactory results with a high Pearson correlation coefficient and adequate errors. Additionally, we modeled the historical ROTI during the modern grand maximum dating back to 1965 and made the prediction during solar cycle 25. In such a way, we can directly compare the climatic variations of the ROTI activity across six solar cycles.

• Paziewski, Jacek; Høeg, Per; Sieradzki, Rafal; Jin, Yaqi; Jarmolowski, Wojciech & Hoque, M. Mainul [Vis alle 12 forfattere av denne artikkelen] (2022). The implications of ionospheric disturbances for precise GNSS positioning in Greenland. Journal of Space Weather and Space Climate. 12. doi: 10.1051/swsc/2022029. Fulltekst i vitenarkiv Vis sammendrag

  Ionospheric irregularities impair Global Navigation Satellite System (GNSS) signals and, in turn, affect the performance of GNSS positioning. Such effects are especially evident at low and high latitudes, which are currently gaining the attention of research and industry sectors. This study evaluates the impact of ionospheric irregularities on GNSS positioning in Greenland. We assess the performance of positioning methods that meet the demands of a wide range of users. In particular, we address the needs of the users of mass-market single-frequency receivers and those who require a solution of high precision provided by geodetic dual-frequency receivers. We take advantage of the datasets collected during three ionospheric storms: the St. Patrick’s Day storm of March 17, 2015, the storm on June 22, 2015, and another on August 25–26, 2018. We discover a significant impact of the ionospheric disturbances on the ambiguity resolution performance and the accuracy of the float solution in Real Time Kinematics (RTK) positioning. Next, assessing the single-frequency ionosphere-free Precise Point Positioning (PPP), we demonstrate that the model is generally unaffected by ionospheric disturbances. Hence, the model is predestined for the application by the users of single-frequency receivers in the areas of frequent ionospheric disturbances. Finally, based on the observation analyses, we reveal that phase signals on the L2 frequency band are more prone to cycle slips induced by ionospheric irregularities than those transmitted on the L1. Such signal properties explain a noticeable decline in the dual-frequency RTK performance during the ionospherically disturbed period and merely no effect for the single-frequency ionosphere-free PPP model.

• Kotova, Daria; Jin, Yaqi & Miloch, Wojciech Jacek (2022). Interhemispheric variability of the electron density and derived parameters by the Swarm satellites during different solar activity. Journal of Space Weather and Space Climate. 12, s. 1–21. doi: 10.1051/swsc/2022007. Fulltekst i vitenarkiv Vis sammendrag

  With the data from the Swarm satellite mission, we study the variability of ionospheric plasma parameters for low and high solar activities. We focus on the electron density measured by Swarm and derived parameters and analyze the variability of these parameters in the contexts of the Northern and Southern hemispheres, specific latitudinal regions, and the solar activity level. We consider two time intervals: with high solar activity (HSA) from August 2014 to July 2015 and with low solar activity (LSA) from January to December 2018. We show that the electron density is described mainly by three probability density functions (PDF): exponentiated Weibull, lognormal, and chi distributions. These results with PDFs can be applied to the modeling or prediction of ionospheric parameters in different regions. The best fit of PDFs was obtained for low and mid-latitudes, while at high latitudes and in the polar caps, the double-peaked features of the distribution require the fit of multiple PDFs. The electron density (Ne) distribution at low latitudes follows more a lognormal distribution, while in the high latitude region, the chi distribution prevails. Different results were obtained for the rate of change of density index (RODI) with two fitting PDFs: lognormal or exponentiated Weibull, where the best fits are for high latitudes and polar caps. We demonstrate high variability in the electron density and derived parameters at low latitudes and in the polar caps. Comparing both hemispheres, we obtained higher values of these parameters during the solar minimum in the Southern hemisphere at high latitudes and polar caps, while for the Northern hemisphere, higher values were obtained at low latitudes. The dependence on the satellite’s altitude was also considered. The main patterns in the diurnal variation of parameters in different regions do not depend on the level of solar activity (which affects only the maximum values). The largest asymmetry between both hemispheres in Ne diurnal distribution was obtained for the polar cap regions. Here a 50% decrease in Ne was observed in the Northern hemisphere during HSA in the early morning sector (04–07 Magnetic Local Time), which has not yet been observed in the Southern hemisphere. For the first time, such a global statistical characterization of the ionospheric plasma density based on the in situ data is presented.

• Kotova, Daria; Jin, Yaqi; Spogli, Luca; Wood, Alan G.; Urbar, Jaroslav & Rawling, James T. [Vis alle 11 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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. [Vis alle 11 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  We investigate the response of the topside ionosphere, auroral and polar sectors, to the forcing of the geospace during September 2017. Specifically, we aim at characterizing such a response in terms of the involved spatial scales and of their intensification during the different auroral and polar cap activity conditions experienced in the selected month, that is characterized by severe geomagnetic storm conditions. For our purposes, we leverage on and compare various in situ plasma density data products provided by the Swarm constellation of the European Space Agency (ESA). The spatio-temporal variability of the involved scales in the plasma density observation is featured through the application of the Fast Iterative Filtering (FIF) signal decomposition technique and, for the first time in the ionospheric field, of a FIF-derived dynamical spectrum called “IMFogram”. The instantaneous time-frequency representation provided through the IMFogram illustrates the time development of the multi-scale processes with spatial and temporal resolutions higher than those obtained with traditional signal processing techniques. To demonstrate this, the IMFogram is tested against Fast Fourier and Continuous Wavelet Transforms. With our fine characterization, we highlight how scale cascading and intensification processes in the plasma density observations follow the ionospheric currents activity, as depicted through the auroral activity and polar cap indices, and through the field-aligned currents data product provided by Swarm.

• Belakhovsky, V.B.; Jin, Yaqi & Miloch, Wojciech Jacek (2022). Dayside Scintillations of GPS Signals According to the Observations on the Svalbard Archipelago. Bulletin of the Russian Academy of Sciences: Physics. ISSN 1062-8738. 86(3), s. 348–353. doi: 10.3103/S1062873822030066. Fulltekst i vitenarkiv
• Zheng, Yuhao; Xiong, Chao; Jin, Yaqi; Liu, Dun; Oksavik, Kjellmar & Xu, Chunyu [Vis alle 11 forfattere av denne artikkelen] (2022). The refractive and diffractive contributions to GPS signal scintillation at high latitudes during the geomagnetic storm on 7-8 September 2017. Journal of Space Weather and Space Climate. 12. doi: 10.1051/swsc/2022036. Fulltekst i vitenarkiv Vis sammendrag

  Different indices have been used to reflect, or monitor the ionospheric scintillation, e.g. the detrended carrier phase, σφ, S4, the rate of change of the vertical total electron content index (vROTI), as well as the ionosphere‐free linear combination (IFLC) of two carrier phases. However, few studies have been performed to investigate the refractive and diffractive contributions to these indices, especially during geomagnetic storms. In this study, we analyze the high-resolution (50 Hz) phase and amplitude measurements from four high-latitude stations in Svalbard, Norway during the geomagnetic storm on 7–8 September 2017. Our results show that at high latitudes, the high-pass filter with a standard cutoff frequency of 0.1 Hz sometimes cannot effectively remove the refraction-driven phase variations, especially during the geomagnetic storm, leading to a remaining refraction contribution to the detrended carrier phase and σφ when scintillation happens. In the meanwhile, as vROTI is sensitive to the TEC gradients, regardless of small- or large-scale ionospheric structures, both refraction and diffraction effects can cause visible fluctuations of vROTI. For most of the scintillation events, the phase indices (including detrended carrier phase, σφ, and vROTI), IFLC, and S4 show consistent fluctuations, indicating that diffraction usually occurs simultaneously with refraction during scintillation. One interesting feature is that although the IFLC and S4 are thought to be both related to the diffraction effect, they do not always show simultaneous correspondence during scintillations. The IFLC is enhanced during the geomagnetic storm, while such a feature is not seen in S4. We suggest that the enhanced IFLC during the geomagnetic storm is caused by the increased high-frequency phase power, which should be related to the enhanced density of small-scale irregularities during storm periods.

• Song, Hosub; Park, Jaeheung; Buchert, Stephan; Jin, Yaqi; Chao, Chi Kuang & Lee, Jaejin [Vis alle 7 forfattere av denne artikkelen] (2022). A Small Peak in the Swarm-LP Plasma Density Data at the Dayside Dip Equator. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 127(7). doi: 10.1029/2022JA030319. Fulltekst i vitenarkiv Vis sammendrag

  In this paper, we statistically investigate an artifact in Langmuir Probe (LP) observations of Swarm satellites. A small peak of electron density (Ne) is frequently found in the Swarm data around the dayside dip equator. On the contrary, they appear in neither the Total Electron Content data of the Swarm/Global Positioning System Receivers nor COSMIC-2 in-situ measurements at similar altitudes but with low orbit inclination. Arguably, this peak does not represent natural ionospheric irregularities but is likely to result from artifacts. The phenomena are found regardless of the season, solar activity, and the velocity direction of the satellite (ascending and descending). They predominantly occur when the magnetic declination is close to zero, that is, when the Swarm ram direction and the Earth's magnetic field are aligned under sunlight. Hence, we attribute the phenomenon to intensified secondary electrons escape when the geomagnetic field lines are normal to conducting surfaces that emit secondary electrons. Since the magnitude of the artifact is only a few percent of the large-scale background, it does not have a serious impact on the value of the Swarm/LP data in scientific research. Nevertheless, future efforts to determine the exact cause of the artifacts will contribute to improving the reliability and quality of plasma density and temperature measured by Swarm/LP.

• Jin, Yaqi; Kotova, Daria; Xiong, Chao; Brask, Steffen Mattias; Clausen, Lasse & Kervalishvili, Guram [Vis alle 8 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv
• Wood, Alan G.; Alfonsi, Lucilla; Clausen, Lasse; Jin, Yaqi; Spogli, Luca & Urbář, Jaroslav [Vis alle 19 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Swarm is the first European Space Agency (ESA) constellation mission for Earth Observation. Three identical Swarm satellites were launched into near-polar orbits on 22 November 2013. Each satellite hosts a range of instruments, including a Langmuir probe, GPS receivers, and magnetometers, from which the ionospheric plasma can be sampled and current systems inferred. In March 2018, the CASSIOPE/e-POP mission was formally integrated into the Swarm mission through ESA’s Earthnet Third Party Mission Programme. Collectively the instruments on the Swarm satellites enable detailed studies of ionospheric plasma, together with the variability of this plasma in space and in time. This allows the driving processes to be determined and understood. The purpose of this paper is to review ionospheric results from the first seven years of the Swarm mission and to discuss scientific challenges for future work in this field.

• Monte-Moreno, Enric; Hernández-Pajares, Manuel; Yang, Heng; Garcia, Rigo Alberto; Jin, Yaqi & Høeg, Per [Vis alle 13 forfattere av denne artikkelen] (2021). Method for Forecasting Ionospheric Electron Content Fluctuations Based on the Optical Flow Algorithm. IEEE Transactions on Geoscience and Remote Sensing. ISSN 0196-2892. doi: 10.1109/TGRS.2021.3126888. Fulltekst i vitenarkiv
• Ivarsen, Magnus Fagernes; St-Maurice, Jean-Pierre; Jin, Yaqi; Park, Jaeheung; Miloch, Wojciech Jacek & Spicher, Andres [Vis alle 8 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Ivarsen, Magnus Fagernes; Park, Jaeheung; Jin, Yaqi & Clausen, Lasse Boy Novock (2021). Ionospheric Plasma Fluctuations Induced by the NWC Very Low Frequency Signal Transmitter. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 126(5). doi: 10.1029/2021JA029213. Fulltekst i vitenarkiv Vis sammendrag

  The Australian NWC (North West Cape) signal transmitter is known to strongly interfere with the topside ionosphere. We analyze 456 conjunctions between Swarm A, B and NWC, in addition to 58 conjunctions between NorSat-1 and NWC. The in-situ measurements provided by these satellites include the 16 Hz Swarm Advanced Plasma Density data set, and the novel 1,000 Hz plasma density measurements from the m-NLP system aboard NorSat-1. We subject the data to a detailed PSD analysis and subsequent superposed epoch analysis. This allows us to present comprehensive statistics of the NWC-induced plasma fluctuations, both their scale-dependency, and their climatology. The result should be seen in the context of VLF signal transmitter-induced plasma density fluctuations, where we find counter-evidence for the existence of turbulent structuring induced by the NWC transmitter.

• 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. Fulltekst i vitenarkiv Vis sammendrag

  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 [Vis alle 7 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  We present a study of decameter scale ionospheric irregularities using in-situ electron density data from the NorSat-1 satellite. During the current period of low solar activity, NorSat-1 frequently observes significant plasma irregularities from several 10 s km down to several decameter. These are often observed near the dayside cusp and dawnside auroral zone. The decameter-scale irregularities are positively correlated with intermediate-scale (10 km) density gradients, for both negative and positive gradients encountered by the satellite. The statistical distribution of electron density over two winter months in the northern hemisphere along NorSat-1 orbits, shows significant density increases in the cusp ionosphere (75°–80° Magnetic LATitude) and in regions near the dawnside auroral oval. Intermediate scale density gradients and small-scale irregularities are clearly associated with these density enhancements. We postulate that these density enhancements and irregularities are due to auroral particle precipitation/plasma dynamics.

• Belakhovsky, Vladimir Borisovich; Jin, Yaqi & Miloch, Wojciech Jacek (2021). Influence of different types of ionospheric disturbances on GPS signals at polar latitudes. Annales Geophysicae. ISSN 0992-7689. 39, s. 687–700. doi: 10.5194/angeo-39-687-2021. Fulltekst i vitenarkiv Vis sammendrag

  Abstract. The comparative research of the influence of different types of auroral particle precipitation and polar cap patches (PCPs) on the global positioning system (GPS) signals disturbances in the polar ionosphere was done. For this purpose, we use the GPS scintillation receivers at Ny-Ålesund and Skibotn, operated by the University of Oslo. The presence of the auroral particle precipitation and polar cap patches was determined by using data from the EISCAT 42m radar on Svalbard. The optical aurora observations in 557.7 and 630.0 nm spectrum lines on Svalbard were used as well for the detection of ionospheric disturbances. The cusp identification was done with using SuperDARN (Hankasalmi) data. We consider events when the simultaneous EISCAT 42m and GPS data were available for the years 2010–2017, and in this paper we present, in detail, typical examples describing the overall picture, and we present the statistics for 120 events. We considered the dayside/cusp precipitation, substorm precipitation, daytime and nighttime PCPs, and precipitation associated with the interplanetary shock wave arrival. We demonstrate that substorm-associated precipitation (even without PCPs) can lead to a strong GPS phase (σϕ) scintillations up to ∼ 1.5–3 radians, which is much stronger than those usually produced by other types of considered ionosphere disturbances. The value of the substorm-phase scintillations in general correlate with the value of the geomagnetic field disturbance. But sometimes even a small geomagnetic substorm, when combined with the PCPs, produces quite strong phase scintillations. Cusp phase scintillations are lower than dayside PCPs scintillations. PCPs can lead to stronger ROT (rate of total electron content) variations than other types of ionosphere disturbances. So our observations suggest that the substorms and PCPs, being different types of the high-latitude disturbances, lead to the development of different types and scales of ionospheric irregularities.

• Zakharov, V.I.; Chernyshov, A.A.; Miloch, Wojciech Jacek & Jin, Yaqi (2020). Influence of the Ionosphere on the Parameters of the GPS Navigation Signals during a Geomagnetic Substorm. Geomagnetism and Aeronomy. ISSN 0016-7932. 60(6), s. 754–767. doi: 10.1134/S0016793220060158. Fulltekst i vitenarkiv
• Jin, Yaqi; Xiong, Chao; Clausen, Lasse Boy Novock; Spicher, Andres; Kotova, Daria & Brask, Steffen [Vis alle 9 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Jin, Yaqi & Xiong, Chao (2020). Interhemispheric asymmetry of large‐scale electron density gradients in the polar cap ionosphere: UT and seasonal variations. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 125(2). doi: 10.1029/2019JA027601. Fulltekst i vitenarkiv Vis sammendrag

  The high‐latitude ionosphere is highly dynamical with significant irregularities and density gradients. However, the spatial and temporal distributions of density gradients and irregularities are very different between the Arctic and Antarctic. In this report, we study the interhemispheric asymmetry of the large‐scale (100 km) density gradients in both polar caps. Our results show that density gradients in the Arctic are enhanced during local winter (December solstice) with a peak around 19 UT. The UT and spatial distributions in the Antarctic local winter (June solstice) are similar to the Arctic except that they are reversed by 12 hr, which indicates a mirror symmetry between hemispheres. The 12‐hr difference in the peak density gradients can be explained by the displacements between the geographic and geomagnetic poles. The only asymmetry (anomaly) is the persistence of strong density gradients in the southern polar cap during local summer (December solstice).

• Belakhovsky, V.B.; Jin, Yaqi & Miloch, Wojciech Jacek (2020). Influence of Different Ionospheric Disturbances on the GPS Scintillations at High Latitudes. Springer Proceedings in Earth and Environmental Sciences. ISSN 2524-342X. s. 281–287. doi: 10.1007/978-3-030-21788-4_24. Fulltekst i vitenarkiv
• Chernyshov, Alexander A.; Miloch, Wojciech Jacek; Jin, Yaqi & Zakharov, Viktor I. (2020). Relationship between TEC jumps and auroral substorm in the high-latitude ionosphere. Scientific Reports. 10. doi: 10.1038/s41598-020-63422-9. Fulltekst i vitenarkiv Vis sammendrag

  The influence of an auroral substorm on the total electron content (TEC) jumps and cycle slips on Global Positioning System (GPS) at high-latitudes is studied. For the first time, optical data from the all-sky imager, as well as interplanetary magnetic field and magnetometer data are used to complete the analysis of the slips occurrence and to monitor the substorm evolution. Two types of slips are considered: (i) instrumental slips including losses in the measured phase of the GPS signal and (ii) sharp TEC variations (TEC jumps) It is demonstrated that the jumps in TEC determined from the GPS signals are mainly related to the auroral particle precipitation that normally occurs during geomagnetic substorms in the polar ionosphere. The GPS frequency L2 is consistently subject to more slips than frequency L1 both for quiet and disturbed conditions. The probability of TEC jumps is higher than for cycle slips in phase at frequencies L1 and L2. The maximum of TEC jumps is observed during the recovery phase of the auroral substorm. Our findings are based on a data set obtained for a particular event. A generalization of the obtained numerical estimates to other events requires additional research and further analysis.

• 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. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Belakhovsky, V.B.; Jin, Yaqi & Miloch, Wojciech Jacek (2020). Influence of the substorm precipitation and polar cap patches on GPS signals at high latitudes. Sovremennye Problemy Distantsionnogo Zondirovaniya Zemli iz Kosmosa. ISSN 2070-7401. 17(6), s. 139–144. doi: 10.21046/2070-7401-2020-17-6-139-144. Fulltekst i vitenarkiv
• Spicher, Andres; Deshpande, Kshitija; Jin, Yaqi; Oksavik, Kjellmar; Zettergren, Matthew D. & Clausen, Lasse Boy Novock [Vis alle 9 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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.

• 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), s. 1570–1583. doi: 10.1029/2019SW002276. Fulltekst i vitenarkiv Vis sammendrag

  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 [Vis alle 10 forfattere av denne artikkelen] (2019). Multineedle Langmuir Probe Operation and Acute Probe Current Susceptibility to Spacecraft Potential. IEEE Transactions on Plasma Science. ISSN 0093-3813. 47(8), s. 3816–3823. doi: 10.1109/TPS.2019.2906377. Fulltekst i vitenarkiv Vis sammendrag

  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), s. 2935–2942. doi: 10.1029/2019JA026500. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Xiong, Chao; Yin, Fan; Luo, Xiaomin; Jin, Yaqi & Wan, Xin (2019). Plasma patches inside the polar cap and auroral oval: The impact on the spaceborne GPS receiver. Journal of Space Weather and Space Climate. 9. doi: 10.1051/swsc/2019028. Fulltekst i vitenarkiv Vis sammendrag

  In this study, we focus on plasma patches with very dense plasma in the southern hemisphere during the main phase of 2015 St. Patrick’s Day storm. With in situ electron densities exceeding 1.5 × 1012 m−3 at 450–500 km altitude, the patches cause strong signal outages of the global positioning system (GPS) receivers on board Swarm satellites. By using the field-aligned currents derived from the Swarm magnetic measurements, we determined whether the satellites fly inside the auroral oval or not. Different influences on the spaceborne GPS receiver are seen when these patches are located at different latitude regions, e.g., inside the polar cap or auroral oval. The simultaneously measurements of 2 Hz electron density as well as 50 Hz magnetic signatures from Swarm show that when large-scale polar cap patches transported from dayside lower latitude entering the cusp region, irregularities with much finer scale-size are generated; associated with various instabilities inside the cusp region, the small-scale irregularities cause much more severe influence on the GPS signals. This is the first direct evidence to show that when plasma patches are located inside the cusp region, the spaceborne receiver experiences stronger outage of GPS signals.

• Han, De-Sheng; Xu, Tong; Jin, Yaqi; Oksavik, Kjellmar; Chen, Xiangcai & Liu, Jian-Jun [Vis alle 9 forfattere av denne artikkelen] (2019). Observational evidence for throat aurora being associated with magnetopause reconnection. Geophysical Research Letters. ISSN 0094-8276. 46(13), s. 7113–7120. doi: 10.1029/2019GL083593. Fulltekst i vitenarkiv Vis sammendrag

  Throat auroras have been suggested to be related to indentations on the subsolar magnetopause. However, the indentation generation process and the resulting ionospheric responses have remained unknown. An EISCAT Svalbard Radar experiment was designed to run with all‐sky cameras, which enabled us for the first time to observe the temporal and spatial evolution of flow reversals, Joule heating, and ion upflows associated with throat aurora. The high‐resolution data enabled us to discriminate that the flow bursts and Joule heating were concurrent and co‐located, but were always observed on the west side of the associated throat auroras, reflecting that the upward/downward field‐aligned currents associated with throat aurora are always to the east/west, respectively. These results are consistent with the geometry of Southwood (1987) flux transfer event model and provide strong evidence for throat aurora being associated with magnetopause reconnection events. The results also support a conceptual model of the throat aurora.

• Jin, Yaqi; Spicher, Andres; Xiong, Chao; Clausen, Lasse Boy Novock; Kervalishvili, Guram & Stolle, Claudia [Vis alle 7 forfattere av denne artikkelen] (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), s. 1262–1282. doi: 10.1029/2018JA026063. Fulltekst i vitenarkiv Vis sammendrag

  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 [Vis alle 8 forfattere av denne artikkelen] (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), s. 7098–7111. doi: 10.1029/2019JA026942. Fulltekst i vitenarkiv Vis sammendrag

  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. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Jin, Yaqi & Oksavik, Kjellmar (2018). GPS Scintillations and Losses of Signal Lock at High Latitudes During the 2015 St. Patrick's Day Storm. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 123(9), s. 7943–7957. doi: 10.1029/2018JA025933. Fulltekst i vitenarkiv Vis sammendrag

  We investigate the Global Positioning System (GPS) amplitude and phase scintillations during a severe geomagnetic storm on 17 March 2015. The auroral oval expanded significantly due to a strongly southward interplanetary magnetic field (Bz was −25 nT). When the auroral oval was over Skibotn in northern Norway, significant enhancements in total electron content (TEC) fluctuations, amplitude, and phase scintillation were observed. The strongest amplitude and phase scintillations were observed when a TEC blob propagated across the field of view. Strong amplitude and phase scintillations were observed near the edges of the TEC blob. The European Incoherent SCATter ultrahigh frequency radar observed significant enhancement of electron density (from 0.8 × 1011 to 1.6 × 1011 m−3) near the edge of the TEC blob in the F2 region, while the E region was only slightly enhanced. This indicates that the plasma processes and instability modes, which accounted for the strong GPS scintillations, should involve the F2 region ionosphere. We also analyzed the tracking performance of the GPS receiver during strong ionospheric scintillation condition. While the receiver maintained tracking of the GPS L1 signal, the strong amplitude scintillation resulted in a power fade up to 12 dB‐Hz. Losses of lock occurred in the GPS L2 band. Both the power fade and rapid phase fluctuation should contribute to losses of lock.

• Miloch, Wojciech Jacek; Jin, Yaqi; Xiong, Chao; Kervalishvili, Guram; Spicher, Andres & Clausen, Lasse Boy Novock [Vis alle 7 forfattere av denne artikkelen] (2018). Ionospheric plasma irregularities studied with Swarm satellites. E3S Web of Conferences. 62, s. 1–6. doi: 10.1051/e3sconf/20186201009. Fulltekst i vitenarkiv Vis sammendrag

  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 [Vis alle 8 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Spicher, Andres; Clausen, Lasse Boy Novock; Miloch, Wojciech Jacek; Lofstad, Victoria; Jin, Yaqi & Moen, Jøran Idar (2017). Interhemispheric study of polar cap patch occurrence based on Swarm in situ data. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. doi: 10.1002/2016JA023750. Fulltekst i vitenarkiv Vis sammendrag

  The Swarm satellites offer an unprecedented opportunity for improving our knowledge about polar cap patches, which are regarded as the main space weather issue in the polar caps. We present a new robust algorithm that automatically detects polar cap patches using in situ plasma density data from Swarm. For both hemispheres, we compute the spatial and seasonal distributions of the patches identified separately by Swarm A and Swarm B between December 2013 and August 2016. We show a clear seasonal dependency of patch occurrence. In the Northern Hemisphere (NH), patches are essentially a winter phenomenon, as their occurrence rate is enhanced during local winter and very low during local summer. Although not as pronounced as in the NH, the same pattern is seen for the Southern Hemisphere (SH). Furthermore, the rate of polar cap patch detection is generally higher in the SH than in the NH, especially on the dayside at about 77° magnetic latitude. Additionally, we show that in the NH the number of patches is higher in the postnoon and prenoon sectors for interplanetary magnetic field (IMF) By<0 and IMF By>0, respectively, and that this trend is mirrored in the SH, consistent with the ionospheric flow convection. Overall, our results confirm previous studies in the NH, shed more light regarding the SH, and provide further insight into polar cap patch climatology. Along with this algorithm, we provide a large data set of patches automatically detected with in situ measurements, which opens new horizons in studies of polar cap phenomena.

• Jin, Yaqi; Moen, Jøran Idar; Oksavik, Kjellmar; Spicher, Andres; Clausen, Lasse Boy Novock & Miloch, Wojciech Jacek (2017). GPS scintillations associated with cusp dynamics and polar cap patches. Journal of Space Weather and Space Climate. 7. doi: 10.1051/swsc/2017022. Fulltekst i vitenarkiv Vis sammendrag

  This paper investigates the relative scintillation level associated with cusp dynamics (including precipitation, flow shears, etc.) with and without the formation of polar cap patches around the cusp inflow region by the EISCAT Svalbard radar (ESR) and two GPS scintillation receivers. A series of polar cap patches were observed by the ESR between 8:40 and 10:20 UT on December 3, 2011. The polar cap patches combined with the auroral dynamics were associated with a significantly higher GPS phase scintillation level (up to 0.6 rad) than those observed for the other two alternatives, i.e., cusp dynamics without polar cap patches, and polar cap patches without cusp aurora. The cusp auroral dynamics without plasma patches were indeed related to GPS phase scintillations at a moderate level (up to 0.3 rad). The polar cap patches away from the active cusp were associated with sporadic and moderate GPS phase scintillations (up to 0.2 rad). The main conclusion is that the worst global navigation satellite system space weather events on the dayside occur when polar cap patches enter the polar cap and are subject to particle precipitation and flow shears, which is analogous to the nightside when polar cap patches exit the polar cap and enter the auroral oval.

Se alle arbeider i NVA

• Jin, Yaqi; Spicher, Andres; Pecseli, Hans Laszlo; Clausen, Lasse; Miloch, Wojciech Jacek & Jacobsen, Knut Stanley [Vis alle 9 forfattere av denne artikkelen] (2024). In-situ observations of plasma blob inside the nightside auroral region and features of small-scale irregularities. Fulltekst i vitenarkiv
• Spicher, Andres; Kvammen, Andreas; Zettergren, Matthew David; Bonnell, John W.; Clausen, Lasse & Deshpande, Kshitija [Vis alle 14 forfattere av denne artikkelen] (2024). Understanding the creation of ionospheric F-region turbulence and its spatio-temporal evolution using GNSS scintillations, auxiliary instruments and modeling. Fulltekst i vitenarkiv Vis sammendrag

  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 [Vis alle 20 forfattere av denne artikkelen] (2024). Characterizing ionospheric turbulence on the poleward side of the cusp using sounding rocket observations and modelling work. Fulltekst i vitenarkiv
• Ivarsen, Magnus Fagernes; Jin, Yaqi & Spicher, Andres (2024). What are the dominant causes of density irregularities in the ionospheric cusp. Fulltekst i vitenarkiv
• Spicher, Andres; Kvammen, Andreas; LaBelle, James; Zettergren, Matthew D.; Bonnell, John W. & Roglans, Roger [Vis alle 20 forfattere av denne artikkelen] (2023). Examining the relevance of different instability mechanisms in causing ionospheric cusp irregularities based on sounding rocket data and numerical simulations. Fulltekst i vitenarkiv
• Enengl, Florine; Spogli, Luca; Kotova, Daria; Jin, Yaqi; Oksavik, Kjellmar & Partamies, Noora [Vis alle 7 forfattere av denne artikkelen] (2023). On the formation of small-scale irregularities driven by auroral particle precipitation. Fulltekst i vitenarkiv
• Ivarsen, Magnus Fagernes; St-Maurice, Jean-Pierre; Hussey, Glenn & Jin, Yaqi (2023). How does auroral morphology affect ionospheric irregularities? Fulltekst i vitenarkiv
• Xiong, Chao; Zheng, Yuhao; Jin, Yaqi; Liu, Dun; Xu, Chunyu & Zhu, Yixun [Vis alle 7 forfattere av denne artikkelen] (2022). Diagnose the diffractive contribution to GNSS scintillation at high latitude during the geomagnetic storm on 7-8 September 2017. Fulltekst i vitenarkiv
• Kotova, Daria; Jin, Yaqi & Miloch, Wojciech Jacek (2022). Erratum: Interhemispheric variability of the electron density and derived parameters by the Swarm satellites during different solar activity (J. Space Weather Space Clim. (2022) 12 (12) DOI: 10.1051/swsc/2022007). Journal of Space Weather and Space Climate. 12. doi: 10.1051/swsc/2022013. Fulltekst i vitenarkiv
• Miloch, Wojciech Jacek; Alfonsi, Lucilla; Spogli, Luca; Urbar, Jaroslav; Cesaroni, Claudio & Cicone, Antonio [Vis alle 15 forfattere av denne artikkelen] (2022). Swarm – VIP: Variability of Ionospheric Plasma studied and modelled based on data from the Swarm satellites. Fulltekst i vitenarkiv
• Jin, Yaqi; Miloch, Wojciech Jacek; Alfonsi, Lucilla; Spogli, Luca; Urbar, Jaroslav & Cesaroni, Claudio [Vis alle 13 forfattere av denne artikkelen] (2022). Variability of Ionospheric Plasma studied and modelled based on data from the Swarm satellites. Fulltekst i vitenarkiv
• Kotova, Daria; Jin, Yaqi; Spogli, Luca; Wood, Alan G.; Urbar, Jaroslav & Rawlings, James T. [Vis alle 11 forfattere av denne artikkelen] (2022). Electron density fluctuations from Swarm as a proxy for ground-based scintillation data: A statistical perspective. Fulltekst i vitenarkiv
• Miloch, Wojciech Jacek; Kotova, Daria & Jin, Yaqi (2022). Ionospheric plasma structuring over Antarctica based on satellite and ground observations. Fulltekst i vitenarkiv
• Enengl, Florine; Kotova, Daria; Jin, Yaqi; Clausen, Lasse & Miloch, Wojciech Jacek (2022). Ionospheric plasma irregularities in relation to dynamic auroral forms. Fulltekst i vitenarkiv
• Kotova, Daria; Jin, Yaqi; Brask, Steffen Mattias; Spogli, Luca; Wood, Alan G. & Miloch, Wojciech Jacek (2022). Comparison of electron density fluctuations measured by Swarm satellites with the ground-based scintillation data. Fulltekst i vitenarkiv
• Spicher, Andres; LaBelle, James William; Bonnell, John W.; Roglans, Roger; Moser, Chrystal & Fuselier, Stephen A. [Vis alle 18 forfattere av denne artikkelen] (2022). Sounding rocket investigation of multi-scale (density) irregularities in the cusp region. Fulltekst i vitenarkiv
• Spicher, Andres; Vierinen, Juha; Oksavik, Kjellmar; Jin, Yaqi; Huyghebaert, Devin Ray & Madhanakumar, Mahith (2022). Multi-instrument multi-scale characterization of ionospheric irregularities in the cusp region. Fulltekst i vitenarkiv
• Kotova, Daria; Jin, Yaqi & Miloch, Wojciech Jacek (2022). Interhemispheric investigation of variability of ionospheric parameters measured by the Swarm satellites for quiet geomagnetic conditions. Fulltekst i vitenarkiv Vis sammendrag

  The use of satellite data allows us to study the variability of ionospheric plasma parameters globally without references to ground stations or receivers in different regions of the Earth. The Swarm mission, which was launched in November 2013 and is still operational, allows us to investigate the effects of decreasing solar activity on ionospheric variability. We use the Swarm in-situ measurements of the electron density and derived parameters that have been combined into a unique dataset called the Ionospheric Plasma IRregularities product (IPIR) [1]. IPIR provides characteristics of the plasma variability along the orbit and gives information on plasma density structures in the ionosphere in terms of their amplitudes, gradients and spatial scales. In this study, we focused on distributions and statistics of these parameters in the Northern and Southern hemispheres for quiet geomagnetic conditions. Our results provide information on the shape of the distribution and probability density functions of electron density and derived ionospheric parameters that can be used as a baseline important for other modeling studies. Understanding the distribution of such parameters in the context of the geomagnetic activity and selected ionospheric regions can have implications for the development of new satellite instruments and for the accuracy of GNSS precise positioning. This work was supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (ERC Consolidator Grant agreement No. 866357, POLAR-4DSpace).

• Kotova, Daria; Jin, Yaqi; Spogli, Luca; Wood, Alan G.; Alfonsi, Lucilla & Urbar, Jaroslav [Vis alle 9 forfattere av denne artikkelen] (2022). Comparison Of Electron Density Fluctuations From Swarm Satellites With The Ground-based Scintillation Data: A Statistical Perspective. Fulltekst i vitenarkiv Vis sammendrag

  The Swarm satellite mission is actively used to conduct various studies of the ionosphere, focusing on such aspects as the electric and magnetic fields or plasma temperature, structuring and irregularities. The mission is a constellation of three satellites that were launched in November 2013 and have been collecting data continuously since then. We use a global product based on the Swarm satellite measurements that characterizes ionospheric irregularities and fluctuations. The IPIR (Ionospheric Plasma IRregularities product) provides in-situ characteristics of plasma density structures in the ionosphere, of plasma irregularities in terms of their amplitudes, gradients and spatial scales and assigns them to geomagnetic regions. Ionospheric irregularities and fluctuations are often the cause increases the error in position, velocity, time determination based on Global Navigation Satellite Systems (GNSS), which signals pass through the ionosphere. The IPIR provides an indication, in the form of a numerical value index, on severity of irregularities for the integrity of trans-ionospheric radio signals and hence the accuracy of GNSS precise positioning. This work demonstrates that data from the Swarm satellite's flyby height can be used as a proxy for ground-based scintillation data. We compare two datasets from Swarm satellites (with 1-second resolution) and from groundbased scintillation receivers (with 1-minute resolution). To consider the measured parameters for the same area, we find time intervals when the Swarm satellites pass over the field of view of the ground-based Global Positioning System (GPS) receiver. A geometry with an elevation angle of 30° above the receiver was used to calculate these passes. We also performed an azimuthal selection of the GNSS data according to Swarm satellite fly. We used only those GPS satellites that flew near the position of the Swarm satellite in azimuth sector ±10°. We provide validations of the IPIR product against the ground-based measurements, focusing on GPS TEC and scintillation data in low and high-latitudes regions in different longitudinal sectors. We calculate median, mean, maximum and standard deviation values for parameters for both dataset for each conjunction point (for each GPS satellite and Swarm). We observe a weak trend of stronger scintillations with an increasing IPIR index, where the IPIR index presents a product of amplitudes and temporal variations in plasma densities.

• Spicher, Andres; Vierinen, Juha; Oksavik, Kjellmar & Jin, Yaqi (2022). Statistical characteristics of ionospheric irregularities in the cusp ionosphere based on multi-instrument techniques. Fulltekst i vitenarkiv Vis sammendrag

  Plasma density irregularities disturbing signals from Global Navigation Satellite Systems (GNSS) are known to be regular features of the high-latitude ionosphere, especially around the cusp and auroral regions. Despite their relevance for society, irregularity formation and evolution are still relatively poorly understood, and observations revealing the spatio-temporal characteristics of ionospheric structuring at different scales are needed to assess the exact mechanism(s) responsible for them. In this study, we focus on data from the European Incoherent Scatter Scientific Association (EISCAT) Svalbard Radars (ESR) operating in fast scanning mode. We use ESR experiments in which the antenna was swept in elevation, and create consecutive two-dimensional images showing how electron density, ion velocity, electron temperature, and ion temperatures change with latitude and time at different altitudes. We present selected events in which the ESR scans are combined with all-sky images and in-situ data from the Swarm satellites to provide multi-scale observations of cusp phenomena comprising polar cap patches, flow channels, particle precipitation, and ion heating. We compare the observations with the presence of GNSS scintillations, allowing to monitor the onset and development of irregularities causing scintillations, and to inspect their connection with the phenomena above-mentioned. We then extend the analysis by performing a statistical study using all ESR fast scans identified between January 2001 and December 2015. We investigate the statistical characteristics of the measured parameters at different altitudes and under different geomagnetic conditions. Overall, this study will provide further insights onto the spatio-temporal evolution of ionospheric cusp dynamics, and on the possible physical sources causing ionospheric irregularities with Space weather impacts.

• Kotova, Daria; Jin, Yaqi & Miloch, Wojciech Jacek (2021). Investigation of interhemispheric variability of ionospheric parameters by the Swarm satellites for different solar activity. Fulltekst i vitenarkiv Vis sammendrag

  The use of satellite data allows us to study the variability of ionospheric plasma parameters globally without references to ground stations or receivers in different regions of the Earth. The Swarm mission, which was launched in 2014 and is still operational, allows us to investigate the effects of decreasing solar activity on the ionospheric variability. In our study, we use the Swarm in-situ measurements of the electron density and derived parameters. This dataset provides characteristics of the plasma variability along the orbit and gives information on plasma density structures in the ionosphere in terms of their amplitudes, gradients and spatial scales. In this study, we focused on the investigation of variability of these parameters in northern and southern hemispheres. Understanding of the distribution of such parameters in the context of the solar activity level and selected ionospheric regions can have implications for the development of new satellite instruments and for the accuracy of GNSS precise positioning.

• Spicher, Andres; Moen, Jøran Idar; LaBelle, James William; Bonnell, John W; Roglans, Roger & Moser, Chrystal [Vis alle 18 forfattere av denne artikkelen] (2021). Sounding rocket studies of ionospheric turbulence above Svalbard. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Miloch, Wojciech Jacek; Alfonsi, Lucilla; Spogli, Luca; Urbar, Jaroslav; Cesaroni, C & Cicone, Antonio [Vis alle 14 forfattere av denne artikkelen] (2021). Variability of ionosphere studied and modelled based on data from the Swarm satellites. Fulltekst i vitenarkiv
• Kotova, Daria; Jin, Yaqi; Brask, Steffen; Cilliers, Pierre & Miloch, Wojciech Jacek (2020). Comparison of characteristics of electron density fluctuations from Swarm satellites with the ground-based scintillation data. Fulltekst i vitenarkiv
• Kotova, Daria; Jin, Yaqi & Miloch, Wojciech Jacek (2020). Variability of ionospheric parameters by the Swarm satellites for different solar activity. Fulltekst i vitenarkiv
• Spicher, Andres; LaBelle, James William; Bonnell, John W; Bounds, Scott; Clausen, Lasse Boy Novock & Mare, Francesca Di [Vis alle 16 forfattere av denne artikkelen] (2020). On multi-scale density irregularities observed by sounding rockets within regions of enhanced scintillations in the cusp ionosphere. Fulltekst i vitenarkiv
• Spicher, Andres; Kletzing, Craig A.; Bounds, Scott; Bonnell, John W.; Roglans, Roger & Fuselier, Stephen A. [Vis alle 21 forfattere av denne artikkelen] (2020). Cusp rocket experiment of density structures. Fulltekst i vitenarkiv
• Miloch, Wojciech Jacek; Alfonsi, Lucilla; Spogli, Luca; Wood, Alan; Sahtahmassebi, Golnaz & Clausen, Lasse [Vis alle 10 forfattere av denne artikkelen] (2020). Variability of Ionospheric Plasma Based on Swarm Satellite Data. Fulltekst i vitenarkiv
• Miloch, Wojciech Jacek; Jin, Yaqi; Xiong, Chao; Brask, Steffen Mattias; Kotova, Daria & Kervalishvili, Guram [Vis alle 9 forfattere av denne artikkelen] (2020). Ionospheric Plasma IRregularities (IPIR data products). Fulltekst i vitenarkiv
• Spicher, Andres; Oksavik, Kjellmar; Jin, Yaqi; Clausen, Lasse Boy Novock; Zettergren, Matthew D. & Deshpande, K. B. [Vis alle 8 forfattere av denne artikkelen] (2019). A reverse flow event as the onset of ionospheric scintillation irregularities in the cusp. Fulltekst i vitenarkiv
• Jin, Yaqi & Oksavik, Kjellmar (2019). Severe GPS Phase and Amplitude Scintillations at High Latitudes During the 2015 St. Patrick’s Day Storm. Fulltekst i vitenarkiv
• Han, Desheng; Xu, Tong; Jin, Yaqi; Oksavik, Kjellmar; Chen, Xiangcai & Liu, J.-J. [Vis alle 9 forfattere av denne artikkelen] (2019). Meso-scale ionospheric flow cells, localized Joule heating, and ion upflow associated with throat aurora as observed by EISCAT. Fulltekst i vitenarkiv
• Spicher, Andres; Oksavik, Kjellmar; Jin, Yaqi; Moen, Jøran Idar; Baddeley, Lisa & Clausen, Lasse Boy Novock (2019). On the sources of Cusp Ionospheric Scintillation Irregularities. Fulltekst i vitenarkiv
• Spicher, Andres; Deshpande, Kshitija; Zettergren, Matthew D.; Oksavik, Kjellmar; Jin, Yaqi & Clausen, Lasse Boy Novock [Vis alle 7 forfattere av denne artikkelen] (2019). Modeling scintillation produced by ionospheric Kelvin Helmholtz in the cusp ionosphere using GEMINI-SIGMA. Fulltekst i vitenarkiv Vis sammendrag

  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 [Vis alle 9 forfattere av denne artikkelen] (2019). Ionospheric plasma irregularities studied globally with the Swarm satellites. Fulltekst i vitenarkiv
• Kotova, Daria; Jin, Yaqi & Miloch, Wojciech Jacek (2019). Comparison of ionospheric plasma irregularities measured by Swarm with the ground-based GPS scintillation data. Fulltekst i vitenarkiv Vis sammendrag

  Ionospheric irregularities are often the cause of GNSS precise positioning errors, as well as disruption of radio communications in the HF range. The reason for the occurrence of these irregularities can be various non-stationary processes in the near-Earth space plasma that depend on the response of the ionosphere to the variations in the near Earth space. Therefore, the study of ionospheric irregularities is an urgent scientific and applied problem. In this study we use a global product based on the Swarm satellite measurements that characterizes ionospheric irregularities and fluctuations. The IPIR (Ionospheric Plasma IRregularities product) provides characteristics of plasma density structures in the ionosphere, of plasma irregularities in terms of their amplitudes, gradients and spatial scales and assigns them to geomagnetic regions and consequently to predominant plasma processes. It also provides indication, in the form of a numerical value index, on their severity for the integrity of trans-ionospheric radio signals and hence the accuracy of GNSS precise positioning. In this work we made validations of the IPIR product against the ground-based measurements, focusing on GPS TEC and scintillation data in low latitudes regions.

• 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. Fulltekst i vitenarkiv
• Jin, Yaqi; Miloch, Wojciech Jacek; Clausen, Lasse Boy Novock; Spicher, Andres; Stolle, Claudia & Kervalishvili, G. [Vis alle 7 forfattere av denne artikkelen] (2018). Ionospheric Plasma Irregularities Characterized by the Swarm satellites. Fulltekst i vitenarkiv
• Jin, Yaqi; Spicher, Andres; Xiong, Chao; Clausen, Lasse Boy Novock; Stolle, Claudia & Kervalishvili, G. [Vis alle 7 forfattere av denne artikkelen] (2018). Detecting high-latitude ionospheric plasma irregularities by Swarm satellites. Fulltekst i vitenarkiv
• Jin, Yaqi & Moen, Jøran Idar (2017). The cusp ionosphere as driven by dayside transient. Fulltekst i vitenarkiv
• Jin, Yaqi (2017). In-situ Measurement of Reversed Flow Event in the Cusp Ionosphere. Fulltekst i vitenarkiv
• 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. Fulltekst i vitenarkiv Vis sammendrag

  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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