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During minor to moderate geomagnetic storms, caused by corotating interaction regions (CIRs) at the leading edge of high-speed streams (HSSs), solar wind Alfven waves modulated the magnetic reconnection at the dayside magnetopause. The Resolute Bay Incoherent Scatter Radars (RISR-C and RISR-N), measuring plasma parameters in the cusp and polar cap, observed ionospheric signatures of flux transfer events (FTEs) that resulted in the formation of polar cap patches. The patches were observed as they moved over the RISR, and the Canadian High-Arctic Ionospheric Network (CHAIN) ionosondes and GPS receivers. The coupling process modulated the ionospheric convection and the intensity of ionospheric currents, including the auroral electrojets. The horizontal equivalent ionospheric currents (EICs) are estimated from ground-based magnetometer data using an inversion technique. Pulses of ionospheric currents that are a source of Joule heating in the lower thermosphere launched atmospheric gravity waves, causing traveling ionospheric disturbances (TIDs) that propagated equatorward. The TIDs were observed in the SuperDual Auroral Radar Network (SuperDARN) high-frequency (HF) radar ground scatter and the detrended total electron content (TEC) measured by globally distributed Global Navigation Satellite System (GNSS) receivers. Canada Foundation for Innovation; New Brunswick Innovation Foundation; national scientific funding agency of Australia; national scientific funding agency of Canada; national scientific funding agency of China; national scientific funding agency of France; national scientific funding agency of Italy; national scientific funding agency of Japan; national scientific funding agency of Norway; national scientific funding agency of South Africa; national scientific funding agency of United Kingdom; national scientific funding agency of United States of America; NSF [AGS-1934997]; National Science Foundation [AGS-1935110]; Canadian Space Agency; Province of Saskatchewan; Canadian Space Agency/Geospace Observatory (GO) Canada program, Athabasca University, Centre for Science/Faculty of Science and Technology; US National Science Foundation [ATM-0827903]; Magnetospheric Physics Program of National Science Foundation [AGS-0245139]; Canadian Space Agency [9 F007-071429, 9 F007-070993]; CSA [21SUSTCHAI]; United Kingdom Natural Environment Research Council (NERC) [NE/W003147/1, NE/W003368/1]; NASA [80NSSC18K0570, 80NSSC18K1220, 80GSFC17C0018, NAS5-02099] Published version Infrastructure funding for CHAIN was provided by the Canada Foundation for Innovation and the New Brunswick Innovation Foundation. CHAIN operation is conducted in collaboration with the Canadian Space Agency (CSA). Contributions by the ACE (Norman F. Nees at Bartol Research Institute, David J. McComas at SWRI), Geotail (Susumu Kokubun at STELAB Nagoya University), Wind spacecraft teams, NASA's SPDF/CDAWeb, and the NSSDC OMNIWeb are acknowledged. RISR-C is funded by the Canada Foundation for Innovation and led by the University of Calgary, University of Saskatchewan, Athabasca University, and SRI International. The authors acknowledge the use of SuperDARN data. SuperDARN is a collection of radars funded by the national scientific funding agencies of Australia, Canada, China, France, Italy, Japan, Norway, South Africa, United Kingdom, and the United States of America. The Christmas Valley SuperDARN radars are maintained and operated by Dartmouth College under support by NSF grant AGS-1934997. Operations of the Goose Bay, Kapuskasing, and Blackstone SuperDARN radars are supported by the National Science Foundation under award AGS-1935110. The operation of the Saskatoon radar is supported by the Canada Foundation for Innovation, the Canadian Space Agency, and the Province of Saskatchewan. We thank the many different groups operating magnetometer arrays for providing data for this study, including the THEMIS UCLA magnetometer network (Ground-based Imager and Magnetometer Network for Auroral Studies). The AUTUMNX magnetometer network is funded through the Canadian Space Agency/Geospace Observatory (GO) Canada program, Athabasca University, Centre for Science/Faculty of Science and Technology. The Magnetometer Array for Cusp and Cleft Studies (MACCS) array is supported by the US National Science Foundation grant ATM-0827903 to Augsburg College. The Solar and Terrestrial Physics (STEP) magnetometer file storage is at the Department of Earth and Planetary Physics, University of Tokyo and maintained by Kanji Hayashi (hayashi@grl.s.u-tokyo.ac.jp).The McMAC Project is sponsored by the Magnetospheric Physics Program of National Science Foundation through grant AGS-0245139. The ground magnetic stations are operated by the Technical University of Denmark, National Space Institute (DTU Space). The Canadian Space Science Data Portal is funded in part by the Canadian Space Agency contract numbers 9 F007-071429 and 9 F007-070993. The Canadian Magnetic Observatory Network (CANMON) is maintained and operated by the Geological Survey of Canada. David R. Themens's contribution to this work is supported in part through CSA grant no. 21SUSTCHAI and through the United Kingdom Natural Environment Research Council (NERC) EISCAT3D: Fine-scale structuring, scintillation, and electrodynamics (FINESSE) (NE/W003147/1) and DRivers and Impacts of Ionospheric Variability with EISCAT-3D (DRIIVE) (NE/W003368/1) projects. James M. Weygand acknowledges NASA grant: 80NSSC18K0570, 80NSSC18K1220, NASA contract: 80GSFC17C0018 (HPDE), NAS5-02099(THEMIS). Shibaji Chakraborty thanks the National Science Foundation for support under grant AGS-1935110.

Solar wind Alfvén waves in high-speed streams from coronal holes modulate dayside ionospheric convection and currents, including auroral electrojets [1]. They generate large- to medium-scale atmospheric gravity waves (AGWs) propagating globally from sources in the lower thermosphere both upward and downward [2,3]. In the upper atmosphere, the AGWs drive traveling ionospheric disturbances (TIDs) observed by the Super Dual Auroral Radar Network (SuperDARN), Poker Flat Incoherent Scatter Radar (PFISR), and the GNSS total electron content (TEC) mapping technique. The horizontal equivalent ionospheric currents are estimated from the ground-based magnetometer data using an inversion technique. In the lower atmosphere, the equatorward propagating AGWs with attenuated amplitudes can be amplified upon over-reflection in the troposphere. They can release conditional symmetric instability leading to slantwise convection, latent heat release and intensification of extratropical cyclones [4,5], which in turn are a source of AGWs/TIDs. Southeastward propagating TIDs that originate from cold fronts of intensifying extratropical cyclones are observed in the detrended TEC maps, and by the multipoint and multifrequency continuous Doppler sounders in Czechia. Ray tracing AGWs in a model atmosphere supports the observations.[1] Prikryl P., et al., Ann. Geophys., 40, 619–639, 2022. doi.org/10.5194/angeo-40-619-2022[2] Mayr H.G., et al., Space Sci. Rev. 54, 297–375, 1990. doi:10.1007/BF00177800[3] Prikryl, P., et al., Ann. Geophys. 23, 401–417, 2005. doi.org/10.5194/angeo-23-401-2005[4] Prikryl P., et al., Ann. Geophys. 27, 31–57, 2009. doi:10.5194/angeo-27-31-2009[5] Prikryl P., et al., J. Atmos. Sol.-Terr. Phys. 171, 94–10, 2018. doi:10.1016/j.jastp.2017.07.023

Extreme (≥ 20 nT/s) geomagnetic disturbances (GMDs, also denoted as MPEs - magnetic perturbation events) – impulsive nighttime disturbances with time scale ~5-10 min, have sufficient amplitude to cause bursts of geomagnetically induced currents (GICs) that can damage technical infrastructure. In this study we present occurrence statistics for extreme GMD events from five stations in the MACCS and AUTUMNX magnetometer arrays in Arctic Canada at magnetic latitudes ranging from 65° to 75°. We report all large (≥ 6 nT/s) and extreme GMDs from these stations from 2011 through 2022 to analyze variations of GMD activity over a full solar cycle and compare them to those found in three earlier studies. GMD activity between 2011 and 2022 did not closely follow the sunspot cycle, but instead was lowest during its rising phase and maximum (2011-2014) and highest during the early declining phase (2015-2017). Most of these GMDs, especially the most extreme, were associated with high-speed solar wind streams (Vsw > 600 km/s) and steady solar wind pressure. All extreme GMDs occurred within 80 min after substorm onsets, but few within 5 min. Multistation data often revealed a poleward progression of GMDs, consistent with a tailward retreat of the magnetotail reconnection region. These observations indicate that extreme GIC hazard conditions can occur for a variety of solar wind drivers and geomagnetic conditions, not only for fast-coronal mass ejection driven storms.

We have examined the most intense external (magnetospheric and ionospheric) and internal (induced) |dH/dt| (amplitude of the 10 s time derivative of the horizontal geomagnetic field) events observed by the high-latitude International Monitor for Auroral Geomagnetic Effects (IMAGE) magnetometers between 1994 and 2018. While the most intense external |dH/dt| events at adjacent stations typically occurred simultaneously, the most intense internal (and total) |dH/dt| events were more scattered in time, most likely due to the complexity of induction in the conducting ground. The most intense external |dH/dt| events occurred during geomagnetic storms, among which the Halloween storm in Oct 2003 featured prominently, and drove intense geomagnetically induced currents (GIC). Events in the prenoon local time sector were associated with sudden commencements (SC) and pulsations, and the most intense |dH/dt| values were driven by abrupt changes in the eastward electrojet due to solar wind dynamic pressure increase or decrease. Events in the premidnight and dawn local time sectors were associated with substorm activity, and the most intense |dH/dt| values were driven by abrupt changes in the westward electrojet, such as weakening and poleward retreat (premidnight) or undulation (dawn). Despite being associated with various event types and occurring at different local time sectors, there were common features among the drivers of most intense external |dH/dt| values: pre-existing intense ionospheric currents (SC events were an exception) that were abruptly modified by sudden changes in the magnetospheric magnetic field configuration. While proper description of the fast changes during SC events appears to require 1 s data, pulsations and substorms may be sufficiently described by 10 s |dH/dt|. 1 min data, however, significantly underestimates the |dH/dt| peaks. Our results contribute towards the ultimate goal of reliable forecasts of dH/dt and GIC.

Nearly all studies of impulsive geomagnetic disturbances (GMDs, also known as magnetic perturbation events MPEs) that can produce dangerous geomagnetically induced currents (GICs) have used data from the northern hemisphere. In this study, we investigated GMD occurrences during the first 6 months of 2016 at four magnetically conjugate high latitude station pairs using data from the Greenland West Coast magnetometer chain and from Antarctic stations in the conjugate AAL-PIP magnetometer chain. Events for statistical analysis and four case studies were selected from Greenland/AAL-PIP data by detecting the presence of >6 nT/s derivatives of any component of the magnetic field at any of the station pairs. For case studies, these chains were supplemented by data from the BAS-LPM chain in Antarctica as well as Pangnirtung and South Pole in order to extend longitudinal coverage to the west. Amplitude comparisons between hemispheres showed (a) a seasonal dependence (larger in the winter hemisphere), and (b) a dependence on the sign of the By component of the interplanetary magnetic field (IMF): GMDs were larger in the north (south) when IMF By was >0 (

Solar wind Alfvén waves [1] coupling to the magnetosphere-ionosphere-thermosphere (MIT) have been associated with high-intensity long-duration continuous auroral electrojet activity [2] and shown to modulate ionospheric convection in the cusp generating polar cap patches and atmospheric gravity waves [3,4]. The Resolute Bay Incoherent Scatter Radars (RISR-C and RISR-N) [5] are well suited for observing the ionospheric signatures of flux transfer events and subsequent polar patch formation in the cusp. During minor to moderate geomagnetic storms caused by corotating interaction regions at the leading edge of solar wind high speed streams polar patches were observed as they convected over the RISR, and the Canadian High-Arctic Ionospheric Network (CHAIN) ionosondes and GPS receivers [6]. The patches were generated by the MIT coupling of Alfvén waves in the upstream solar wind. The coupling process modulated the ionospheric convection and the intensity of ionospheric currents, including auroral electrojets. The horizontal equivalent ionospheric currents and vertical current amplitudes are estimated from the ground-based magnetometer data using an inversion technique [7]. Pulses of ionospheric currents that are a source of Joule heating in the lower thermosphere launched atmospheric gravity waves causing traveling ionospheric disturbances (TIDs) propagating equatorward. TIDs were observed in the SuperDARN HF radar ground scatter [8], in the detrended GPS TEC maps, and in one case, in the altitude profiles of ionospheric electron densities observed by the Poker Flat ISR [9].[1] Belcher, JW, Davis, L, Jr. 1971. J. Geophys. Res. 76, 3534–3563.[2] Tsurutani, BT, Gonzalez, WD. 1987. Planet. Space Sci. 35(4), 405–412.[3] Prikryl, P, et al., 1999. Ann. Geophys. 17, 463–489.[4] Prikryl, P, et al., 2005. Ann. Geophys. 23, 401–417.[5] Gillies RG, et al., 2016. Radio Sci., 51(10):1645-1659.[6] Jayachandran, PT, et al., 2009. Radio Sci., 44, RS0A03.[7] Weygand, JM, et al., 2011. J. Geophys. Res. 116, A03305.[8] Chisham, G., et al., 2007. Surv. Geophys. 28, 33–109.[9] Heinselman, CJ, Nicolls, MJ, 2008. Radio Sci., 43, RS5013.

Electron injections are critical processes associated with magnetospheric substorms, which deposit significant electron energy into the ionosphere. Although wave scattering of $, 25 pages, 5 figures, with supporting information, the manuscript has been accepted for publication by JGR space physics

The Antarctic and Arctic regions are Earth's open windows to outer space. They provide unique opportunities for investigating the troposphere–thermosphere–ionosphere–plasmasphere system at high latitudes, which is not as well understood as the mid- and low-latitude regions mainly due to the paucity of experimental observations. In addition, different neutral and ionised atmospheric layers at high latitudes are much more variable compared to lower latitudes, and their variability is due to mechanisms not yet fully understood. Fortunately, in this new millennium the observing infrastructure in Antarctica and the Arctic has been growing, thus providing scientists with new opportunities to advance our knowledge on the polar atmosphere and geospace. This review shows that it is of paramount importance to perform integrated, multi-disciplinary research, making use of long-term multi-instrument observations combined with ad hoc measurement campaigns to improve our capability of investigating atmospheric dynamics in the polar regions from the troposphere up to the plasmasphere, as well as the coupling between atmospheric layers. Starting from the state of the art of understanding the polar atmosphere, our survey outlines the roadmap for enhancing scientific investigation of its physical mechanisms and dynamics through the full exploitation of the available infrastructures for radio-based environmental monitoring.

The impact of interplanetary shocks on the magnetosphere can trigger magnetic substorms that intensify auroral electrojet currents. These currents enhance ground magnetic field perturbations (d$B$/d$t$), which in turn generate geomagnetically induced currents (GICs) that can be detrimental to power transmission infrastructure. We perform a comparative study of d$B$/d$t$ variations in response to two similarly strong shocks, but with one being nearly frontal, and the other, highly inclined. Multi-instrument analyses by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) and Los Alamos National Laboratory spacecraft show that nightside substorm-time energetic particle injections are more intense and occur faster in the case of the nearly head-on impact. The same trend is observed in d$B$/d$t$ variations recorded by THEMIS ground magnetometers. THEMIS all-sky imager data show a fast and clear poleward auroral expansion in the first case, which does not clearly occur in the second case. Strong field-aligned currents computed with the spherical elementary current system (SECS) technique occur in both cases, but the current variations resulting from the inclined shock impact are weaker and slower compared to the nearly frontal case. SECS analyses also reveal that geographic areas with d$B$/d$t$ surpassing the thresholds 1.5 and 5 nT/s, usually linked to high-risk GICs, are larger and occur earlier due to the symmetric compression caused by the nearly head-on impact. These results, with profound space weather implications, suggest that shock impact angles affect the geospace driving conditions and the location and intensity of the subsequent d$B$/d$t$ variations during substorm activity., 44 pages, 18 figures, 3 tables

As it was recently predicted, the kinetic ballooning/interchange instability (BICI) can provoke reconnection onsets that lead to detached azimuthally thin earthward intrusions (heads) of depleted plasma tubes when 𝛽eq ⩽ 100. Such detached BICI heads would be seen as localized earthward-propagating dipolarization fronts. Using Time History of Events and Macroscale Interactions during Substorms observations in the plasma sheet at XGSM ≈ −11 Re and conjugate All-Sky Imager and magnetometer networks observations on the ground, we show four examples when prominent dipolarization fronts with moderate earthward flows were observed amidst azimuthally drifting interchange heads and concurrently with the ionospheric current intensifications near Time History of Events and Macroscale Interactions during Substorms footprints and auroral bright spots originating from dimmer azimuthal beads/rays. These events support the idea that some of the BICI heads detach from the region with reversed radial gradient of Bz. The de...

We employ Magnetospheric Multiscale, Geostationary Operational Environmental and Los Alamos National Laboratory satellites, as well as the ground magnetometer networks over Greenland and North Amer...

The southward pointing field of view of the Canadian component of the Resolute Bay Incoherent Scatter Radar (RISR-C) is well suited for observing the ionospheric signatures of flux transfer events and subsequent polar patch formation in the cusp. The fast azimuthally oriented flows and associated density depletions often show an enhanced ion temperature from Joule heating caused by the sudden change in plasma flow direction. The newly formed polar patches are then observed as they propagate through the field-of-views of both RISR-C and RISR-N. In the ionosphere, the electron density gradients imposed in the cusp, and small-scale irregularities resulting from gradient-drift instability, particularly in the trailing edges of patches, cause GPS TEC and phase variations, and sometimes amplitude scintillation. The neutral atmosphere is affected by ionospheric currents resulting in Joule heating. The pulses of ionospheric currents in the cusp launch atmospheric gravity waves (AGWs) causing traveling ionospheric disturbances, as they propagate equatorward and upward. On the other hand, the downward propagating AGW packets can impact the lower atmosphere, including the troposphere. Despite significantly reduced wave amplitudes, but subject to amplification upon over-reflection in the upper troposphere, these AGWs can trigger/release existing moist instabilities, initiating convection and latent heat release, the energy leading to intensification of storms.

In this study, we investigate ionospheric responses, including currents and aurorae, to solar wind dynamic pressure (SW Pdyn) sudden increases, which are critical for understanding solar wind‐magnetosphere‐ionosphere coupling. We focus on two similar SW Pdyn pulse events that occurred on 24 January 2012 and 12 November 2010. In both cases, equivalent ionospheric currents (EIC) vortices were generated within about ten minutes after the pressure pulse arrival, with a counter‐clockwise rotating vortex (viewed from above) observed on the dusk side in the former case, and a clockwise vortex observed on the dawn side in the latter. Simultaneous ground‐based All‐Sky Imager (ASI) observations in the vicinity of the observed EIC vortex in each case showed that aurorae intensified on the dusk side, and diminished on the dawn side. These observations provide direct evidence of the scenario proposed byShi et al. (2014) that magnetospheric flow vortices generated by a solar wind pressure pulse carry field‐aligned currents into the ionosphere and thereby modulate auroral activity. The dawn/dusk asymmetry in the auroral intensification is a direct result of the opposite sense of vortex rotation on the dawn and dusk sides, which generate oppositely directed field‐aligned currents into/out of the ionosphere.

High-speed streams (HSS) from coronal holes dominate solar wind structure in the absence of coronal mass ejections during solar minimum and the descending branch of solar cycle. Prominent and long-lasting coronal holes produce intense co-rotating interaction regions (CIR) on the leading edge of high-speed plasma streams that cause recurrent ionospheric disturbances and geomagnetic storms. Through solar wind coupling to the magnetosphere-ionosphere-atmosphere (MIA) system they affect the ionosphere and neutral atmosphere at high latitudes, and, at mid to low latitudes, by the transmission of the electric fields [1] and propagation of atmospheric gravity waves from the high-latitude lower thermosphere [2].The high-latitude ionospheric structure, caused by precipitation of energetic particles, strong ionospheric currents and convection, results in changes of the GPS total electron content (TEC) and rapid variations of GPS signal amplitude and phase, called scintillation [3]. The GPS phase scintillation is observed in the ionospheric cusp, polar cap and auroral zone, and is particularly intense during geomagnetic storms, substorms and auroral breakups. Phase scintillation index is computed for a sampling rate of 50 Hz by specialized GPS scintillation receivers from the Canadian High Arctic Ionospheric Network (CHAIN). A proxy index of phase variation is obtained from dual frequency measurements of geodetic-quality GPS receivers sampling at 1 Hz, which include globally distributed receivers of the RT-IGS network that are monitored by the Canadian Geodetic Survey in near-real-time [4]. Temporal and spatial changes of TEC and phase variations following the arrivals of HSS/CIRs [5] are investigated in the context of ionospheric convection and equivalent ionospheric currents derived from a ground magnetometer network using the spherical elementary current system method [6,7].The Joule heating and Lorentz forcing in the high-latitude lower thermosphere have long been recognized as sources of internal atmospheric gravity waves (AGWs) [2] that propagate both upward and downward, thus providing vertical coupling between atmospheric layers. In the ionosphere, they are observed as traveling ionospheric disturbances (TIDs) using various techniques, e.g., de-trended GPS TEC maps [8].In this paper we examine the influence on the Earth’s ionosphere and atmosphere of a long-lasting HSS/CIRs from recurrent coronal holes at the end of solar cycles 23 and 24. The solar wind MIA coupling, as represented by the coupling function [9], was strongly increased during the arrivals of these HSS/CIRs. [1] Kikuchi, T. and K. K. Hashimoto, Geosci. Lett. , 3:4, 2016.[2] Hocke, K. and K. Schlegel, Ann. Geophys., 14, 917–940, 1996.[3] Prikryl, P., et al., J. Geophys. Res. Space Physics, 121, 10448–10465, 2016.[4] Ghoddousi-Fard et al., Advances in Space Research, 52(8), 1397-1405, 2013.[5] Prikryl et al. Earth, Planets and Space, 66:62, 2014.[6] Amm O., and A. Viljanen, Earth Planets Space, 51, 431–440, 1999.[7] Weygand J.M., et al., J. Geophys. Res., 116, A03305, 2011.[8] Tsugawa T., et al., Geophys. Res. Lett., 34, L22101, 2007.[9] Newell P. T., et al., J. Geophys. Res., 112, A01206, 2007.

Formation of thin current sheets in Earth's magnetotail is a critical element of the magnetosphere dynamics. The configuration and stability of these thin current sheets control the onset of magnetic reconnection and particle acceleration in the magnetotail during substorms and other geomagnetic activities. In recent years, multipoint observations, kinetic and hybrid simulations have significantly improved our understanding of the structure and dynamics of thin current sheets, including their ion kinetic physics. Global hybrid simulations have also revealed many details of ion kinetics in thin current sheet physics. In this paper we review current understanding of current sheet physics and discuss our recent observational and simulation results on thin current sheet formation, emphasizing the kinetics of current sheet thinning, multi-component ion populations, the role of electron anisotropy and ion agyrotropy, and the role of the ionosphere.

We examined how much large-scale and localized upward and downward currents contribute to the substorm current wedge (SCW), and how they evolve over time, using the THEMIS all-sky imagers (ASIs) and ground magnetometers. One type of events is dominated by a single large-scale wedge, with upward currents over the surge and broad downward currents poleward-eastward of the surge. The other type of events is a composite of large-scale wedge and wedgelets associated with streamers, with each wedgelet having comparable intensity to the large-scale wedge currents. Among 17 auroral substorms with wide ASI coverage, the composite current type is more frequent than the single large-scale wedge type. The dawn–dusk size of each wedgelet is ~ 600 km in the ionosphere (~ 3.2 RE in the magnetotail, comparable to the flow channel size). We suggest that substorms have more than one type of SCW, and the composite current type is more frequent.

Temporal and spatial changes of GPS total electron content (TEC) and phase variation, called phase scintillation, during auroral substorms and breakups are investigated in the context of horizontal equivalent ionospheric currents and estimated vertical current amplitudes derived from ground magnetometer network using the spherical elementary current method. GPS phase scintillation is computed for sampling rate of 50 Hz by specialized GPS scintillation receivers from the Canadian High Arctic Ionospheric Network (CHAIN). A proxy phase scintillation index is obtained from dual frequency measurements of geodetic-quality GPS receivers sampling at 1 Hz, which include globally distributed receivers of RT-IGS network that are monitored by the Canadian Geodetic Survey in near-real-time. Based on analysis of four cases, it is shown that GPS phase scintillation maps to regions of strong westward electrojet and to the poleward edge of the eastward electrojet. For substorm onsets, auroral breakups and substorm intensifications, the ionospheric pierce points with moderate to strong phase scintillation associated with TEC enhancements map to regions of intense westward electrojet interfacing with the eastward electrojet near the boundaries between downward Region 1 and upward Region 1/Region 2 currents in the Harang discontinuity region, where intense auroral emission was observed for some of the cases studied. Energetic particle precipitation in this dynamic region results in steep electron density gradients and drifting irregularities that are the cause of GPS phase variation.

著者人数: 102名（所属. 宇宙航空研究開発機構宇宙科学研究所 (JAXA)(ISAS): 松岡, 彩子; 篠原, 育; 浅村, 和史), Accepted: 2018-12-29, 資料番号: SA1180350000

Using multipoint data from three Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites, we report a magnetospheric flow vortex driven by a negative solar wind dynamic pressure pulse. The observed vortex rotated in a direction opposite to that associated with positive solar wind dynamic pressure pulses. The vortex was moving tailward, as confirmed by a global magnetohydrodynamics (MHD) simulation. In addition, the equivalent ionospheric currents (EICs) deduced from ground magnetometer station data reveal that a current vortex in the ionosphere near the foot point of the satellites has a rotation sense consistent with that observed in the magnetosphere. The field-aligned current (FAC) density estimated from three THEMIS satellites is about 0.15nA/m(2), and the total FAC of the vortex is about 1.5-3x10(5)A, on the order of the total FAC in a pseudobreakup, but less than the total FAC in most moderate substorms, 10(6)A. Key Points