Journal of Geophysical Research: Space Physics最新文献

{"title":"Statistical Study of Energy Transport and Conversion in Electron Diffusion Regions at Earth's Dayside Magnetopause","authors":"Naïs Fargette,&nbsp;Jonathan P. Eastwood,&nbsp;Cara L. Waters,&nbsp;Marit Øieroset,&nbsp;Tai D. Phan,&nbsp;David L. Newman,&nbsp;J. E. Stawarz,&nbsp;Martin V. Goldman,&nbsp;Giovanni Lapenta","doi":"10.1029/2024JA032897","DOIUrl":"https://doi.org/10.1029/2024JA032897","url":null,"abstract":"<p>The electron diffusion region (EDR) is a key region for magnetic reconnection, but the typical energy transport and conversion in EDRs is still not well understood. In this work, we perform a statistical study of 80 previously published near X-line events identified at the dayside magnetopause in Magnetospheric Multiscale data. We find 44 events that clearly present all commonly accepted EDR signatures and use this database to investigate energy flux partition and energy conversion. We find that energy partition is changed inside EDRs, with a 71%–29% allocation of particle energy flux density between electrons and ions respectively. The electron enthalpy flux density is found to dominate locally at all EDRs and is predominantly oriented in the out-of-plane direction, perpendicular to the reconnecting magnetic field. We also examine the transition from electron- to ion-dominated energy flux partition further from the EDR, finding this typically occurs at scales of the order of the ion inertial length, larger than the typical EDR size. We then investigate energy conversion and transport and highlight complex processes, with potential non-steady-state energy accumulation and release near the EDR. We discuss the implications of our results for reconnection energy conversion, and for magnetopause dynamics in general.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 10","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA032897","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142429238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Waves and Instabilities in Saturn's Magnetosheath: 2. Dispersion Relation Analysis","authors":"I. Cheng,&nbsp;N. Achilleos,&nbsp;X. Blanco-Cano,&nbsp;C. Bertucci,&nbsp;P. Guio","doi":"10.1029/2024JA032585","DOIUrl":"https://doi.org/10.1029/2024JA032585","url":null,"abstract":"&lt;p&gt;The WHAMP (Rönnmark, 1982, https://inis.iaea.org/search/search.aspx?orig_q=RN:14744092) and LEOPARD (Astfalk &amp; Jenko, 2017, https://doi.org/10.1002/2016ja023522) dispersion relation solvers were used to evaluate the growth rate and scale size for mirror mode (MM) and ion cyclotron (IC) instabilities under plasma conditions resembling Saturn's magnetosheath in order to compare observations to predictions from linear kinetic theory. Instabilities and waves are prevalent in planetary magnetosheaths. Understanding the origin and conditions under which different instabilities grow and dominate can help shed light on the role each instability plays in influencing the plasma dynamics of the region. For anisotropic plasmas modeled with bi-Maxwellian particle distribution, the dispersion, growth rate, and scale size of MM and IC were studied as functions of proton temperature anisotropy, proton plasma beta, and oxygen ion abundance. The dispersion solvers showed that the IC mode dominated over MM under typical conditions in Saturn's magnetosheath, but that MM could dominate for high enough &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;mo&gt;+&lt;/mo&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${O}^{+}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; abundance &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mfenced&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;&gt;&lt;/mo&gt;\u0000 &lt;mn&gt;40&lt;/mn&gt;\u0000 &lt;mi&gt;%&lt;/mi&gt;\u0000 &lt;mspace&gt;&lt;/mspace&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;n&lt;/mi&gt;\u0000 &lt;mi&gt;e&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/mfenced&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $left( &gt; 40% {mathrm{n}}_{mathrm{e}}right)$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;. These water ion-rich plasma conditions are occasionally found in Saturn's magnetosheath (Sergis et al., 2013, https://doi.org/10.1002/jgra.50164). The maximum linear growth rates &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mfenced&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;γ&lt;/mi&gt;\u0000 &lt;mi&gt;m&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;mo&gt;/&lt;/mo&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;Ω&lt;/mi&gt;\u0000 &lt;mi&gt;p&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/mfenced&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $left({gamma }_{m}/{{Omega }}_{p}right)$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; for MM ranged from 0.02 to 0.2, larger than","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 10","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA032585","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142429267","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Omnidirectional Energetic Electron Fluxes From 150 to 20,000 km: An ELFIN-Based Model","authors":"Emile Saint-Girons,&nbsp;Xiao-Jia Zhang,&nbsp;Didier Mourenas,&nbsp;Anton V. Artemyev,&nbsp;Vassilis Angelopoulos","doi":"10.1029/2024JA032977","DOIUrl":"https://doi.org/10.1029/2024JA032977","url":null,"abstract":"<p>The strong variations of energetic electron fluxes in the Earth's inner magnetosphere are notoriously hard to forecast. Developing accurate empirical models of electron fluxes from low to high altitudes at all latitudes is therefore useful to improve our understanding of flux variations and to assess radiation hazards for spacecraft systems. In the present work, energy- and pitch-angle-resolved precipitating, trapped, and backscattered electron fluxes measured at low altitude by Electron Loss and Fields Investigation (ELFIN) CubeSats are used to infer omnidirectional fluxes at altitudes below and above the spacecraft, from 150 to 20,000 km, making use of adiabatic transport theory and quasi-linear diffusion theory. The inferred fluxes are fitted as a function of selected parameters using a stepwise multivariate optimization procedure, providing an analytical model of omnidirectional electron flux along each geomagnetic field line, based on measurements from only one spacecraft in low Earth orbit. The modeled electron fluxes are provided as a function of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>L</mi>\u0000 </mrow>\u0000 <annotation> $L$</annotation>\u0000 </semantics></math>-shell, altitude, energy, and two different indices of past substorm activity, computed over the preceding 4 hr or 3 days, potentially allowing to disentangle impulsive processes (such as rapid injections) from cumulative processes (such as inward radial diffusion and wave-driven energization). The model is validated through comparisons with equatorial measurements from the Van Allen Probes, demonstrating the broad applicability of the present method. The model indicates that both impulsive and time-integrated substorm activity partly control electron fluxes in the outer radiation belt and in the plasma sheet.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 10","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142429268","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Plasmoids and Magnetic Field Dipolarizations During Juno's First 47 Orbits: Is Ion Acceleration Always Observed in the Dipolarizations?","authors":"A. Blöcker,&nbsp;E. A. Kronberg,&nbsp;E. E. Grigorenko,&nbsp;R. W. Ebert,&nbsp;G. Clark","doi":"10.1029/2024JA032853","DOIUrl":"https://doi.org/10.1029/2024JA032853","url":null,"abstract":"<p>Plasmoids and magnetic field dipolarizations are reconnection-related phenomena often resulting in reconfiguration of the magnetic field and energetic particle acceleration in planetary magnetotail. Building on the work of Blöcker et al. (2023) (10.1029/2023JA031312), we selected seven specific events from their magnetic field dipolarization analysis, each exhibiting distinct ion dynamics during the time interval of the magnetic field dipolarizations. To gain further insights into the understanding why certain events were associated with ion intensity variations while others were not, we analyzed plasma moments, specifically ion flow velocity and density, for these selected events. Our findings revealed that certain magnetic field dipolarizations within our database exhibit sub-Alfvénic flows and lack the properties typically associated with reconnection-related magnetic field dipolarizations. These magnetic field dipolarizations also do not accelerate ions. Furthermore, we present a survey of Jovian plasmoids and magnetic field dipolarizations during the first 47 orbits of Juno. Applying Juno magnetic field data, we identified 119 magnetic field dipolarizations and 94 plasmoids within a local time range of 18:00–06:00. The majority of plasmoids were detected in the predawn sector, whereas magnetic field dipolarizations were observed closer to Jupiter and were not limited to a specific local time. Combining the statistics of plasmoids and dipolarizations is useful for contextualizing them within the framework of reconnection.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 10","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA032853","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142429259","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Study of the Weddell Sea Anomaly Using Novel Satellite Altimeter TEC Maps","authors":"F. Azpilicueta,&nbsp;B. Nava","doi":"10.1029/2024JA032457","DOIUrl":"https://doi.org/10.1029/2024JA032457","url":null,"abstract":"<p>The Weddell Sea Anomaly (WSA) is a phenomenon of unique intensity and geographic extent that occurs in December (Southern Hemisphere summer) over the southeastern Pacific and southwestern Atlantic oceans regions. Historically, the classic definition of the WSA refers to a situation in which the midnight NmF2 (or TEC) values are greater than the noon NmF2 (or TEC) values. However, several articles published in the last decades have shown that the WSA is a much more complex phenomenon, and its definition might need to be reformulated. This paper presents a phenomenological description of the WSA using a novel type of vertical Total Electron Content (TEC) maps, obtained from altimeter satellite TEC data. The focus of this study is on the possible connection between the WSA and the unexpected expansion and contraction periods observed on the Equatorial Ionospheric Anomaly (EIA) throughout the Southern Hemisphere. The data analysis revealed that the WSA is only one of a number of observed anomalies. Furthermore, we show a significant correlation between the behavior of the EIA and the Y component of the geomagnetic field, which maximizes in the WSA region. We then present a possible hypothesis for interpreting these results.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 10","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428914","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of Subauroral Polarization Streams on Ionospheric Radial Currents During the Geomagnetic Storm on 23 April 2023","authors":"Hao Xia,&nbsp;Hui Wang,&nbsp;Kedeng Zhang","doi":"10.1029/2024JA032783","DOIUrl":"https://doi.org/10.1029/2024JA032783","url":null,"abstract":"<p>Using observations from dual-spacecraft (dual-SC, Swarm <i>A</i> and <i>C</i>) and simulations from the Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIEGCM), this work investigates the ionospheric radial current (IRC) in response to subauroral polarization streams (SAPS) during the geomagnetic storm on 23 April 2023. At noon, a radially inward disturbance IRC (ΔIRC) emerges in response to SAPS, leading to a further intensification of inward IRC. The model simulation indicates that the dynamo current prevails over the polarization current, serving as the primary driver of the inward ΔIRC. Additionally, the significantly enhanced Pedersen conductivity potentially amplifies the inward ΔIRC. At dusk, ΔIRC exhibit a slight outward trend before 21 UT and a pronounced inward trend around 21–24 UT. This temporal variation is attributed to the equatorward propagation of SAPS-induced thermospheric winds within 3–4 hr. The noontime inward electric field at the dip equator arises from both equatorward winds at low-mid latitudes and local eastward winds. However, at dusk, the inward polarization electric field primarily stems from local disturbed eastward winds.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 10","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142430401","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impact of EMIC Waves on Electron Flux Dropouts Measured by GPS Spacecraft: Insights From ELFIN","authors":"Didier Mourenas,&nbsp;Anton V. Artemyev,&nbsp;Xiao-Jia Zhang,&nbsp;Vassilis Angelopoulos","doi":"10.1029/2024JA032984","DOIUrl":"https://doi.org/10.1029/2024JA032984","url":null,"abstract":"<p>Although the effects of electromagnetic ion cyclotron (EMIC) waves on the dynamics of the Earth's outer radiation belt have been a topic of intense research for more than 20 years, their influence on rapid dropouts of electron flux has not yet been fully assessed. Here, we make use of contemporaneous measurements on the same <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>L</mi>\u0000 </mrow>\u0000 <annotation> $L$</annotation>\u0000 </semantics></math>-shell of trapped electron fluxes at 20,000 km altitude by Global Positioning System (GPS) spacecraft and of trapped and precipitating electron fluxes at 450 km altitude by Electron Losses and Fields Investigation (ELFIN) CubeSats in 2020–2022, to investigate the impact of EMIC wave-driven electron precipitation on the dynamics of the outer radiation belt below the last closed drift shell of trapped electrons. During six of the seven selected events, the strong 1–2 MeV electron precipitation measured at ELFIN, likely driven by EMIC waves, occurs within 1–2 hr from a dropout of relativistic electron flux at GPS spacecraft. Using quasi-linear diffusion theory, EMIC wave-driven pitch angle diffusion rates are inferred from ELFIN measurements, allowing us to quantitatively estimate the corresponding flux drop based on typical spatial and temporal extents of EMIC waves. We find that EMIC wave-driven electron precipitation alone can account for the observed dropout magnitude at 1.5–3 MeV during all events and that, when dropouts extend down to 0.5 MeV, a fraction of electron loss may sometimes be due to EMIC waves. This suggests that EMIC wave-driven electron precipitation could modulate dropout magnitude above 1 MeV in the heart of the outer radiation belt.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 10","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA032984","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142430310","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Extent of the Magnetotail of Venus From the Solar Orbiter, Parker Solar Probe and BepiColombo Flybys","authors":"Niklas J. T. Edberg,&nbsp;David J. Andrews,&nbsp;J. Jordi Boldú,&nbsp;Andrew P. Dimmock,&nbsp;Yuri V. Khotyaintsev,&nbsp;Konstantin Kim,&nbsp;Moa Persson,&nbsp;Uli Auster,&nbsp;Dragos Constantinescu,&nbsp;Daniel Heyner,&nbsp;Johannes Mieth,&nbsp;Ingo Richter,&nbsp;Shannon M. Curry,&nbsp;Lina Z. Hadid,&nbsp;David Pisa,&nbsp;Luca Sorriso-Valvo,&nbsp;Mark Lester,&nbsp;Beatriz Sánchez-Cano,&nbsp;Katerina Stergiopoulou,&nbsp;Norberto Romanelli,&nbsp;David Fischer,&nbsp;Daniel Schmid,&nbsp;Martin Volwerk","doi":"10.1029/2024JA032603","DOIUrl":"https://doi.org/10.1029/2024JA032603","url":null,"abstract":"&lt;p&gt;We analyze data from multiple flybys by the Solar Orbiter, BepiColombo, and Parker Solar Probe (PSP) missions to study the interaction between Venus' plasma environment and the solar wind forming the induced magnetosphere. Through examination of magnetic field and plasma density signatures we characterize the spatial extent and dynamics of Venus' magnetotail, focusing mainly on boundary crossings. Notably, we observe significant differences in boundary crossing location and appearance between flybys, highlighting the dynamic nature of Venus' magnetotail. In particular, during Solar Orbiter's third flyby, extreme solar wind conditions led to significant variations in the magnetosheath plasma density and magnetic field properties, but the increased dynamic pressure did not compress the magnetotail. Instead, it is possible that the increased EUV flux at this time rather caused it to expand in size. Key findings also include the identification of several far downstream bow shock (BS), or bow wave, crossings to at least 60 &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;R&lt;/mi&gt;\u0000 &lt;mi&gt;V&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{R}}_{V}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; (1 &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;R&lt;/mi&gt;\u0000 &lt;mi&gt;V&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{R}}_{V}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; = 6,052 km is the radius of Venus), and the induced magnetospheric boundary to at least &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;∼&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${sim} $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; 20 &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;R&lt;/mi&gt;\u0000 &lt;mi&gt;V&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{R}}_{V}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;. These crossings provide insight into the extent of the induced magnetosphere. Pre-existing models from Venus Express were only constrained to within &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;∼&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${sim} $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; 5 &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;R&lt;/mi&gt;\u0000 &lt;mi&gt;V&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{R}}_{V}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; of the planet, and we provide modifications to better fit the far-downstream crossings. The new model BS is now significantly closer to t","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 10","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142360001","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of Vertical Shear in the Zonal Wind on Equatorial Electrojet Sidebands: An Observational Perspective Using Swarm and ICON Data","authors":"J. Sreelakshmi,&nbsp;Astrid Maute,&nbsp;Arthur D. Richmond,&nbsp;Geeta Vichare,&nbsp;Brian J. Harding,&nbsp;Patrick Alken","doi":"10.1029/2024JA032678","DOIUrl":"https://doi.org/10.1029/2024JA032678","url":null,"abstract":"<p>The wind dynamo in the ionosphere leads to differential motion of ions and electrons, which in turn sets up electric fields and currents. Observations show that daytime lower thermospheric horizontal winds have large vertical gradients. Numerical modeling conducted approximately 50 years ago demonstrated that the zonal wind shears in the ∼130–180 km altitude range can generate off-equatorial relative minima (dips) in the daytime height-integrated eastward current density, appearing as westward sidebands north and south of the equatorial electrojet (EEJ). This study observationally confirms this connection for the first time by combining Ionospheric CONnection explorer zonal wind profiles and Swarm latitudinal zonal currents. We demonstrate observationally that the magnitude of the EEJ sideband current is proportional to the strength of westward turning winds with altitude in the Pedersen conductivity dominated region. Additional numerical experiments explain the importance of wind shear in different altitude regions in generating the sideband current. This study contributes to the better understanding of the neutral wind effect on the local current generation.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 10","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142359999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of Superthermal Plasmas on Hiss Wave-Driven Scattering Loss of Radiation Belt Electrons","authors":"Xin Ma,&nbsp;Qi Zhu,&nbsp;Yuequn Lou,&nbsp;Xing Cao,&nbsp;Binbin Ni,&nbsp;Shuqin Chen,&nbsp;Taifeng Jin","doi":"10.1029/2024JA032808","DOIUrl":"https://doi.org/10.1029/2024JA032808","url":null,"abstract":"<p>Plasmaspheric hiss plays an important role in the loss of radiation belt electrons via cyclotron resonant interactions. The cold plasma approximation is widely used in the evaluation of hiss-driven electron losses, which however can break down during disturbed periods of geomagnetic storms and substorms. The kappa particle velocity distribution, characterized by a pronounced high-energy tail, is well-established to model the profile of superthermal plasma under disturbed geomagnetic conditions. In the present study, by calculating the electron bounce-averaged pitch angle diffusion coefficients with kappa plasma dispersion relations, we investigate the sensitivity of hiss-induced cyclotron-resonant electron scattering loss to the spectral index <i>κ</i> under a variety of superthermal plasma conditions. Our results demonstrate that, with increasing <i>κ</i>, the diffusion coefficients of ∼20–100 keV radiation belt electrons significantly decrease at lower pitch angles and increase at higher pitch angles. In contrast, for electrons at higher energies, the diffusion coefficients tend to increase at lower pitch angles and decrease at relatively higher pitch angles. We also find that decrease of <i>L</i>-shell and increase of <i>α</i>* and temperature anisotropy tend to weaken the hiss-driven pitch angle scattering efficiency of electrons at energies from tens to hundreds of keV with a dip at ∼30–50 keV, while the scattering of higher energy electrons can be enhanced. This study confirms the important role of superthermal plasmas in the hiss-driven electron loss processes and should be carefully incorporated in future modeling of radiation belt electron dynamics.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 10","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142360000","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}