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• Ivarsen, Magnus Fagernes; St-Maurice, Jean Pierre; Hussey, Glenn C.; McWilliams, Kathryn; Jin, Yaqi & Huyghebaert, Devin Ray [Show all 8 contributors for this article] (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. Full text in Research Archive
• Ivarsen, Magnus Fagernes; St-Maurice, Jean Pierre; Hussey, Glenn C.; Billet, Daniel; Huyghebaert, Devin Ray & Jin, Yaqi [Show all 17 contributors for this article] (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. Full text in Research Archive Show summary

  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.

• Madhanakumar, Mahith; Spicher, Andres; Huyghebaert, Devin Ray; Kashcheyev, Anton; Spogli, Luca & Oksavik, Kjellmar [Show all 9 contributors for this article] (2025). Co‐Ordinated Observations of Multi‐Scale Irregularities Using ICEBEAR and GNSS During the May 2024 Superstorm. Space Weather. 23(8). doi: 10.1029/2025sw004411. Full text in Research Archive Show summary

  We present observations of plasma structuring from three meters up to hundreds of kilometers at auroral latitudes during the extreme geomagnetic storm of May 2024 using co‐ordinated observations from ICEBEAR and Global Navigation Satellite Systems (GNSS) receivers. Intense irregularities on all spatial scales co‐existed for about 4 hr between magnetic latitudes on 10 May during the storm's expansion phase when dense plasma structures and particle precipitation were simultaneously present at the dayside. Irregularities with scales of the order of few hundred meters remained weak thereafter following the depletion of the high latitude ionosphere even though particle precipitation was still ongoing. On the other hand, three meter E‐region irregularities and kilometer scale gradients persisted for about 24 hr, suggesting that both dayside and nightside auroral dynamics contributed to their sustained production. With the absence of an enhanced density reservoir and the region of particle precipitation shifted to higher latitudes, we observed a significant depletion in the irregularity occurrence across all scales in the dayside auroral region on 11 May.

• Ivarsen, Magnus Fagernes; Miyashita, Yukinaga; St-Maurice, Jean-Pierre; Hussey, Glenn C.; Pitzel, Brian & Galeschuk, Draven [Show all 19 contributors for this article] (2025). Characteristic E-Region Plasma Signature of Magnetospheric Wave-Particle Interactions. Physical Review Letters. ISSN 0031-9007. 134(14). doi: 10.1103/PhysRevLett.134.145201. Full text in Research Archive
• Ivarsen, Magnus Fagernes; Gillies, Megan D.; Huyghebaert, Devin Ray; St-Maurice, Jean-Pierre; Lozinsky, Adam & Galeschuk, Draven [Show all 8 contributors for this article] (2024). Turbulence Embedded Into the Ionosphere by Electromagnetic Waves. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 129(8). doi: 10.1029/2023JA032310. Full text in Research Archive Show summary

  When charged particles are accelerated from Earth's magnetosphere and precipitate into the atmosphere, their impact with neutral gas creates the aurora. Structured electric fields drive the acceleration processes but they are also passed down to the ionosphere, meaning that turbulence can in part be embedded into the ionosphere rather than emerge through instability processes locally. Applying a point-cloud analysis technique adapted from observational cosmology, we show how observed turbulence in the ionosphere matches electrical current signatures in the pulsating aurora in a series of conjunctions between space- and ground-based instruments. We propose that the temporal spectrum of pulsations in the pulsating aurora is the driver of a clearly observed energy injection into the ionosphere's unstable bottomside. Precipitating electrons produce electric fields through charge deposition, and we observe wave characteristics that are present in this pattern. Next, the relative electron-ion drifts excite the Farley-Buneman instability, the distribution of whose waves are organized according to the local electric field. It is the temporal characteristics of chorus wave interactions in the magnetosphere that is imparted, via precipitating electrons, to the pulsating aurora, and so we propose that chorus wave interactions are capable of embedding turbulent structure into the ionosphere. This structure (now pressure gradients) dissipate energy in the E-region through turbulent processes, observed by the icebear coherent scatter radar.

• Ivarsen, Magnus Fagernes; Huyghebaert, Devin Ray; Gillies, Megan D.; St-Maurice, Jean-Pierre; Themens, David R. & Oppenheim, Meers [Show all 12 contributors for this article] (2024). Turbulence Around Auroral Arcs. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 129(8). doi: 10.1029/2023JA032309. Full text in Research Archive Show summary

  The spectacular visual displays from the aurora come from curtains of excited atoms and molecules, impacted by energetic charged particles. These particles are accelerated from great distances in Earth's magnetotail, causing them to precipitate into the ionosphere. Energetic particle precipitation is associated with currents that generate electric fields, and the end result is a dissipation of the hundreds of gigawatts to terrawatts of energy injected into Earth's atmosphere during geomagnetic storms. While much is known about how the aurora dissipates energy through Joule heating, little is known about how it does so via small-scale plasma turbulence. Here we show the first set of combined radar and optical images that track the position of this turbulence, relative to particle precipitation, with high spatial precision. During two geomagnetic storms occurring in 2021, we unambiguously show that small-scale turbulence (several meters) is preferentially created on the edges of auroral forms. We find that turbulence appears both poleward and equatorward of auroral forms, as well as being nestled between auroral forms in the north-south direction. These measurements make it clear that small scale auroral plasma turbulence is an integral part of the electrical current system created by the aurora, in the sense that turbulent transport around auroral forms enhances ionospheric energy deposition through Joule heating while at the same time reducing the average strength of the electric field.

• Billett, D.D.; Sartipzadeh, Kian; Ivarsen, Magnus Fagernes; Iorfida, E.; Doornbos, E. & Eyiguler, Eyiguler Kalafatoglu [Show all 8 contributors for this article] (2024). The 2022 Starlink Geomagnetic Storms: Global Thermospheric Response to a High-Latitude Ionospheric Driver. Space Weather. 22(2). doi: 10.1029/2023SW003748. Full text in Research Archive Show summary

  In this study, we present ionospheric observations of field-aligned currents from AMPERE and the ESA Swarm A satellite, in conjunction with high-resolution thermospheric density measurements from accelerometers on board Swarm C and GRACE-FO, for the third and 4 February 2022 geomagnetic storms that led to the loss of 38 Starlink internet satellites. We study the global storm time response of the thermospheric density enhancements, including their decay and latitudinal distribution. We find that the thermospheric density enhances globally in response to high-latitude energy input from the magnetosphere-solar wind system and takes at least a full day to recover to pre-storm density levels. We also find that the greatest density perturbations occur at polar latitudes consistent with the magnetosphere-ionosphere dayside cusp, and that there appeared to be a saturation of the thermospheric density during the geomagnetic storm on the fourth. Our results highlight the critical importance of high-latitude ionospheric observations when diagnosing potentially hazardous conditions for low-Earth-orbit satellites.

• Goodwin, Lindsay Victoria; Ivarsen, Magnus Fagernes; Lamarche, Leslie; Perry, Gareth W. & Negrea, C (2024). Using RISR-N to Resolve Variations in Dayside and Nightside Plasma Density Spatial-Scales. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 129(11). doi: 10.1029/2024JA032482. Full text in Research Archive
• Ivarsen, Magnus Fagernes; St-Maurice, Jean-Pierre; Jin, Yaqi; Park, Jaeheung; Buschmann, Lisa Marie & Clausen, Lasse (2024). To what degree does a high-energy aurora destroy F-region irregularities? Frontiers in Astronomy and Space Sciences. 11. doi: 10.3389/fspas.2024.1309136. Full text in Research Archive Show summary

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

• Buschmann, Lisa Marie; Clausen, Lasse; Spicher, Andres; Ivarsen, Magnus Fagernes & Miloch, Wojciech Jacek (2024). Statistical Studies of Plasma Structuring in the Auroral Ionosphere by the Swarm Satellites. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 129(2). doi: 10.1029/2023JA032097. Full text in Research Archive Show summary

  This study uses over 2 years of 16 Hz density measurements, 50 Hz magnetic field data and ROTI data from the Swarm mission to perform long term statistics of plasma structuring in the polar ionosphere. The timeframe covers more than 2 years near the 24th solar cycle peak. We additionally use 3 years of data obtained from a timeframe close to solar minimum for discussion. We present power spectral densities (PSD) of electron density irregularities and magnetic field for 1‐min intervals. These PSD have been characterized by the probability of a slope steepening, and by integrating the power deposited within frequency intervals corresponding to kilometer scales. For the electron density, we observe seasonal dependencies for both the integrated power and slope characteristics. While the dual slope probability, especially within the polar cap, varies with solar EUV‐radiation, the integrated power is strongest around the equinoxes. Additionally, while we found similar results for the slope probability for both hemispheres, the integrated power exhibits strong hemispheric asymmetries with stronger enhancements within local summer in the southern hemisphere. The ROTI data shows a similar seasonal variability as the density PSD integrated power, in both seasonal dependency and interhemispheric variability. However, for the ROTI data the strongest fluctuations were found within the nightside auroral oval and the cusp. For the PSD of the magnetic field data, we obtain the strongest enhancements within the cusp for all seasons and all hemispheres. The fluctuations may indicate an increase in Alfvénic energy associated with a downward Poynting flux.

• 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. Full text in Research Archive Show summary

  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.

• Ivarsen, Magnus Fagernes; St‐Maurice, Jean-Pierre; Huyghebaert, Devin Ray; Gillies, D. Megan; Lind, Frank & Pitzel, Brian [Show all 7 contributors for this article] (2024). Deriving the Ionospheric Electric Field From the Bulk Motion of Radar Aurora in the E-Region. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 129(11). doi: 10.1029/2024JA033060. Full text in Research Archive Show summary

  In the auroral E‐region strong electric fields can create an environment characterized by fast plasma drifts. These fields lead to strong Hall currents which trigger small‐scale plasma instabilities that evolve into turbulence. Radio waves transmitted by radars are scattered off of this turbulence, giving rise to the ‘radar aurora’. However, the Doppler shift from the scattered signal does not describe the F‐region plasma flow, the E × B drift imposed by the magnetosphere. Instead, the radar aurora Doppler shift is typically limited by nonlinear processes to not exceed the local ion‐acoustic speed of the E‐region. This being stated, recent advances in radar interferometry enable the tracking of the bulk motion of the radar aurora, which can be quite different and is typically larger than the motion inferred from the Dopplershift retrieved from turbulence scatter. We argue that the bulk motion inferred from the radar aurora tracks the motion of turbulent source regions (provided by auroras). This allows us to retrieve the electric field responsible for the motion of field tubes involved in auroral particle precipitation, since the precipitating electrons must E × B drift. Through a number of case studies, as well as a statistical analysis, we demonstrate that, as a result, the radar aurora bulk motion is closely associated with the high‐latitude convection electric field. We conclude that, while still in need of further refinement, the method of tracking structures in the radar aurora has the potential to provide reliable estimates of the ionospheric electric field that are consistent with nature.

• Ivarsen, Magnus Fagernes; St‐Maurice, Jean-Pierre; Hussey, Glenn C.; Huyghebaert, Devin Ray & Gillies, D. Megan (2024). Point-cloud clustering and tracking algorithm for radar interferometry. Physical Review E (PRE). ISSN 2470-0045. 110(4). doi: 10.1103/PhysRevE.110.045207. Full text in Research Archive Show summary

  In data mining, density-based clustering, which entails classifying datapoints according to their distributions in some space, is an essential method to extract information from large datasets. With the advent of software-based radio, ionospheric radars are capable of producing unprecedentedly large datasets of plasma turbulence backscatter observations, and new automatic techniques are needed to sift through them. We present an algorithm to automatically identify and track clusters of radar echoes through time, using dbscan, a celebrated density-based clustering method for noisy point clouds. We demonstrate our algorithm's efficiency by tracking turbulent structures in the E-region ionosphere, the so-called radar aurora. Through conjugate auroral imagery, as well as in situ satellite observations, we demonstrate that the observed turbulent structures generally track the motion of auroras. What is more, the radar aurora bulk motions exhibit key qualities of auroral electric field enhancements that have previously been observed with various instruments. We present preliminary statistical results using our method, and briefly discuss the method's limitations and potential future adaptations.

• St-Maurice, Jean-Pierre; Huyghebaert, Devin Ray; Ivarsen, Magnus Fagernes & Hussey, Glenn C. (2023). Narrow Width Farley-Buneman Spectra Above 100 km Altitude. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 128(10). doi: 10.1029/2022JA031191. Full text in Research Archive Show summary

  Abstract For spectra associated with full turbulence the observed mean phase velocity of unstable Farley‐Buneman waves has been found not to exceed the ion‐acoustic speed, c s . This has been attributed to various nonlinear processes. However, weakly turbulent modes are also excited on the edge of the “instability cone.” These modes have to be actual eigenmodes predicted by linear instability theory near‐threshold conditions. Unlike the modes that are associated with strong turbulence, these weakly turbulent modes are affected by the ion drift. This can make the Doppler shift of narrow spectra reach as high as the E  ×  B drift velocity in the upper portion of the unstable layer at small aspect angles. Slow narrow spectra are also predicted nearer the E direction. We have produced a model of the Doppler shift of narrow‐width spectra under various electric field conditions above 100 km altitude. While the fluid dispersion relation is used to clarity the physics, we have also found the eigenmodes from an accepted kinetic dispersion relation. The calculations include a new model of the ion‐acoustic speed based on an empirical model of the electron temperature and of ion frictional heating under strong electric field conditions. The model provides an explanation for various VHF observations of the Doppler shift of narrow spectra that have been called “Type III spectra” and “Type IV spectra” in the existing literature.

• 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. Full text in Research Archive Show summary

  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.

• Huyghebaert, Devin Ray; Chau, Jorge L.; Spicher, Andres; Ivarsen, Magnus Fagernes; Clahsen, Matthias & Latteck, Ralph [Show all 7 contributors for this article] (2023). Investigating Spatial and Temporal Structuring of E-Region Coherent Scattering Regions Over Northern Norway. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 128(10). doi: 10.1029/2023JA031682. Full text in Research Archive Show summary

  Recently, it has been shown that the Spread Spectrum Interferometric Multistatic meteor radar Observing Network radar system located in northern Norway is capable of measuring ionospheric E-region coherent scatter with spatial and temporal resolutions on the order of 1.5 km and 2 s, respectively. Four different events from June and July of 2022 are examined in the present study, where the coherent scatter measurements are used as a tracer for large-scale ionospheric phenomena such as plasma density enhancements and ionospheric electric fields. By applying a two-dimensional Fourier analysis to range-time-intensity data, we perform a multi-scale spatial and temporal investigation to determine the change in range over time of large-scale ionospheric structures (>3 km) which are compared with line-of-sight velocities of the small scale structures (∼5 m) determined from the Doppler shift of the coherent scatter. The spectral characteristics of the large-scale structures are also investigated and logarithmic spectral slopes for scale sizes of 100–10 km were found to be between −3.0 and −1.5. This agrees with much of the previous work on the spatial spectra scaling for ionospheric electric fields. This analysis aids in characterizing the source of the plasma turbulence and provides crucial information about how energy is redistributed from large to small scales in the E-region ionosphere.

• Ivarsen, Magnus Fagernes; Lozinsky, Adam; St-Maurice, Jean-Pierre; Spicher, Andres; Huyghebaert, Devin Ray & Hussey, Glenn C. [Show all 9 contributors for this article] (2023). The Distribution of Small-Scale Irregularities in the E-Region, and Its Tendency to Match the Spectrum of Field-Aligned Current Structures in the F-Region. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 128(5). doi: 10.1029/2022JA031233. Full text in Research Archive Show summary

  We associate new data from icebear, a coherent scatter radar located in Saskatchewan, Canada, with scale-dependent physics in the ionosphere. We subject the large-scale icebear 3D echo patterns (treated as 2D point clouds) to a data analysis technique hitherto never applied to the ionosphere, a technique that is widely applied in cosmological red-shift surveys to characterize the spatial clustering of galaxies. The technique results in a novel method to calculate the spatial power spectral density of the greater ionospheric irregularity field. We compare results from this method to in-situ plasma density and magnetic field observations from the Swarm mission. We show that there is a remarkable similarity between echo clustering spectra in the E-region and the field-aligned current structuring spectrum observed in the F-region: a clear and characteristic preferred scale (5 km) both in the E- and F-region spectra. We discuss the possibility that this represents evidence of an energy injection into the ionospheric irregularity field via energetic particle precipitation, but offer alternative interpretations with wider connotations for the ionosphere-magnetosphere system. These findings open new and promising avenues of research for the study of the location of ionospheric scatter echoes with 3D information. It constitutes a novel way to consider the pattern of ionospheric irregularities over wide fields of view when there is an abundance of radar echoes, which allows for the analysis of radar data as point clouds.

• Ivarsen, Magnus Fagernes; St-Maurice, Jean-Pierre; Hussey, Glenn C.; Galeschuk, Draven; Lozinsky, Adam & Pitzel, Brian [Show all 7 contributors for this article] (2023). An Algorithm to Separate Ionospheric Turbulence Radar Echoes From Those of Meteor Trails in Large Data Sets. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 128(1). doi: 10.1029/2022JA031050. Full text in Research Archive Show summary

  Abstract Coherent scatter echoes from disintegrating meteors and from the unstable ionospheric E‐region can overlap considerably between 90 and 110 km altitudes. As the physical origin of plasma irregularities produced by meteor trails differs starkly from that of E‐region auroral irregularities, this has consequences for winds as well as electrodynamic studies, thereby introducing a need to distinguish between the two types of echoes. To that goal, we have developed a novel separation algorithm to automatically sort through arbitrarily large data sets in the region of overlap. This proves very useful when the 3D location of echoes is available. The algorithm uses a definition of crowding, or clustering, in both time and space and has been developed and tested with a comprehensive data set obtained from the recently built Canadian icebear 3D radar. We discuss the characteristics belonging to the two classes of echoes, and present statistical results about the location of each type of echo as a function of conditions. Our proposed algorithm can be applied to any coherent scatter echo data with high resolution 3D location information.

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

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

• Huyghebaert, Devin Ray; Billett, Daniel; Chartier, Alex; Chau, Jorge L.; Hussey, Glenn C. & Hysell, David L. [Show all 11 contributors for this article] (2022). The future of auroral E-region plasma turbulence research. Frontiers in Astronomy and Space Sciences. 9. doi: 10.3389/fspas.2022.1062358. Full text in Research Archive Show summary

  The heating caused by ionospheric E-region plasma turbulence has documented global implications for the energy transfer from space into the terrestrial atmosphere. Traveling atmospheric disturbances, neutral wind motion, energy deposition rates, and ionospheric conductance have all been shown to be potentially affected by turbulent plasma heating. Therefore it is proposed to enhance and expand existing ionospheric radar capabilities and fund research into E-region plasma turbulence so that it is possible to more accurately quantify the solar-terrestrial energy budget and study phenomena related to E-region plasma turbulence. The proposed research funding includes the development of models to accurately predict and model the E-region plasma turbulence using particle-in-cell analysis, fluidbased analysis, and hybrid combinations of the two. This review provides an expanded and more detailed description of the past, present, and future of auroral E-region plasma turbulence research compared to the summary report submitted to the National Academy of Sciences Decadal Survey for Solar and Space Physics (Heliophysics) 2024–2033 (Huyghebaert et al., 2022a).

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

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

• Ivarsen, Magnus Fagernes; St-Maurice, Jean-Pierre; Jin, Yaqi; Park, Jaeheung; Miloch, Wojciech Jacek & Spicher, Andres [Show all 8 contributors for this article] (2021). Steepening Plasma Density Spectra in the Ionosphere: The Crucial Role Played by a Strong E-Region. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 126(8). doi: 10.1029/2021JA029401. Full text in Research Archive Show summary

  Based on the Swarm 16 Hz Advanced Plasma Density data set, and using the Swarm A satellite, we apply automatic detection of spectral breaks in seven million sampled plasma density power spectra in the high-latitude F-region ionosphere. This way, we survey the presence of plasma irregularity dissipation due to an enhanced E-region conductance, caused both by solar photoionization and particle precipitation. We introduce a new quantity named the steepening slope index (SSI) which we use to estimate the occurrence rate of break-points in sampled plasma densities. We provide an interpretation of SSI in the context of solar photoionization-induced conductance enhancements of the E-region. We present a comprehensive climatology of the SSI occurrence rate, along with statistics documenting characteristic high-latitude plasma density spectra. In the absence of steepening, the typical spectral index is 2.1. When density spectra steepen, the index is typically 1.6 at large scales, and 2.7 at small scales. We discuss the impact of high-energy deeply penetrating electron precipitation in the diffuse aurora, and precipitating electrons in the aurora at large. Here, a key finding is that near the cusp, where the F-region conductance is enhanced, spectra tend not to steepen. We find that both the diffuse and discrete aurora are modulating F-region plasma irregularity dissipation through an enhancement of E-region conductance, highlighting the role played by factors other than solar zenith angle in high-latitude plasma dynamics. The influence of E-region conductance on spectral shapes indicates the need for a new discussion of how particle precipitation can structure the local winter high-latitude F-region ionosphere.

• 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. Full text in Research Archive Show summary

  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. Full text in Research Archive Show summary

  We present an investigation of polar cap plasma structure lifetimes. We analyze both simulated data from ionospheric models (International Reference Ionosphere model and Mass Spectrometer Incoherent Scatter model) and in situ data from the Swarm satellite mission (the 16 Hz Advanced Plasma Density dataset). We find that the theoretical prediction that E-region conductance is a predictor of F-region polar cap plasma structure lifetimes is indeed supported by both in situ-based observations and by ionospheric models. In situ plasma structure lifetimes correlate well with the ratio of F- to E-region conductance. We present explicit predictions of small scale (∼1 km) structure lifetimes, which range from less than 1 h during local summer to around 3 h during local winter. We highlight a large discrepancy between the observational and theoretical scale-dependency of decay due to diffusion.

• Jin, Yaqi; Clausen, Lasse; Spicher, Andres; Ivarsen, Magnus Fagernes; Zhang, Yongliang & Miloch, Wojciech Jacek [Show all 7 contributors for this article] (2021). Statistical Distribution of Decameter Scale (50 m) Ionospheric Irregularities at High Latitudes. Geophysical Research Letters. ISSN 0094-8276. 48(19). doi: 10.1029/2021GL094794. Full text in Research Archive Show summary

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

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

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

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

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

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

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

• Ivarsen, Magnus Fagernes; Bull, Philip James; Llinares, Claudio & Mota, David (2016). Distinguishing screening mechanisms with environment-dependent velocity statistics. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 595. doi: 10.1051/0004-6361/201628604. Full text in Research Archive

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• Madhanakumar, Mahith; Spicher, Andres; Huyghebaert, Devin Ray; Kashcheyev, Anton; Spogli, Luca & Oksavik, Kjellmar [Show all 9 contributors for this article] (2025). Observations of irregularities with scales from 3 meters to several hundreds of kilometers during the May 2024 Superstorm | CEDAR. doi: https:/cedarscience.org/sites/default/files/2025-posters/irri-11-mahith-madhanakumar-poster-2.pdf. Full text in Research Archive
• Huyghebaert, Devin Ray; Chau, Jorge Luis; Hussey, Glenn C.; St‐Maurice, Jean-Pierre; Ivarsen, Magnus Fagernes & Clahsen, Matthias [Show all 8 contributors for this article] (2024). Comparison of E-region Coherent Scatter Statistics at 49.5 MHz and 32.55 MHz with ICEBEAR and SIMONe Norway. Full text in Research Archive
• Ivarsen, Magnus Fagernes; Jin, Yaqi & Spicher, Andres (2024). What are the dominant causes of density irregularities in the ionospheric cusp. Full text in Research Archive
• Ivarsen, Magnus Fagernes (2024). The Bulk Motions of the Radar Aurora: Automatic Tracking of Turbulent Structures. Full text in Research Archive
• Ivarsen, Magnus Fagernes; Huyghebaert, Devin Ray & Gillies, D. Megan (2024). The Auroral Arc and Plasma Turbulence. Full text in Research Archive
• Ivarsen, Magnus Fagernes (2024). The apparent motion of auroral plasma turbulence. Full text in Research Archive
• Ivarsen, Magnus Fagernes (2024). The Auroral Arc and its Accompanying Plasma Turbulence. Full text in Research Archive
• Ivarsen, Magnus Fagernes (2024). A Case for Turbulent Structure being Directly Embedded into the Ionosphere. Full text in Research Archive
• Ivarsen, Magnus Fagernes (2024). Deriving an Electric Field from the Radar Aurora Bulk Motions. Full text in Research Archive
• Ivarsen, Magnus Fagernes (2024). The role of soft electrons in sculpting the cusp irregularity landscape. Full text in Research Archive
• Ivarsen, Magnus Fagernes (2024). The Chaos that Surrounds the Aurora. Full text in Research Archive
• Ivarsen, Magnus Fagernes & Hussey, Glenn C. (2024). The shape of plasma turbulence in the lower ionosphere: a point-cloud approach. Full text in Research Archive
• Ivarsen, Magnus Fagernes (2024). What is the role of particle precipitation in producing plasma turbulence in the cusp? Full text in Research Archive
• Huyghebaert, Devin Ray; Chau, Jorge L.; Spicher, Andres; Ivarsen, Magnus Fagernes; Clausen, Matthias & Latteck, Ralph [Show all 7 contributors for this article] (2023). Large Scale Temporal and Spatial Characteristics of E-region Plasma Irregularities Measured by SIMONe Norway. Full text in Research Archive
• Ivarsen, Magnus Fagernes (2023). Remarkable similarity between the clustering spectrum of 3-meter waves in the E-region and field-aligned current structuring in the F-region. Full text in Research Archive
• Ivarsen, Magnus Fagernes (2023). What ICEBEAR 3D echo detection rates reveal about Ionospheric Plasma Turbulence and its origin. Full text in Research Archive
• Ivarsen, Magnus Fagernes (2023). What is the Role of Soft Precipitation in the Cusp. Full text in Research Archive
• Ivarsen, Magnus Fagernes (2023). The tendency (or lack thereof) for radar echoes from the aurora to match observations from space. Full text in Research Archive
• Ivarsen, Magnus Fagernes; St‐Maurice, Jean-Pierre & Hussey, Glenn C. (2023). Measuring Small-scale Turbulence in the High-latitude E- and F-regions Simultaneously. Full text in Research Archive
• Ivarsen, Magnus Fagernes (2023). Auroral Arcs and the Radio Aurora. Full text in Research Archive
• Ivarsen, Magnus Fagernes; St-Maurice, Jean-Pierre; Hussey, Glenn & Jin, Yaqi (2023). How does auroral morphology affect ionospheric irregularities? Full text in Research Archive
• Ivarsen, Magnus Fagernes (2023). What is the role of soft precipitation in the cusp? Full text in Research Archive
• Ivarsen, Magnus Fagernes (2022). The dissipation of F region ionospheric irregularities. Full text in Research Archive
• Ivarsen, Magnus Fagernes (2022). Coherent scatter radar: Separating meteor trail echoes from ionospheric scatter. Full text in Research Archive
• Ivarsen, Magnus Fagernes (2021). Plasma Irregularity Dissipation in the F-Region Ionosphere. Universitetet i Oslo. Full text in Research Archive
• Ivarsen, Magnus Fagernes; Lilje, Per Barth & Mota, David (2016). Distinguishing screening mechanisms with environment-dependent velocity statistics. Universitetet i Oslo. Full text in Research Archive

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