Journal of Geophysical Research: Space Physics最新文献

{"title":"Global Occurrence Morphology of Higher Band ECH Waves in the Magnetosphere Derived From MMS Observations","authors":"Aojun Ren,&nbsp;Jiang Yu,&nbsp;Xiaoman Liu,&nbsp;Jing Wang,&nbsp;Zuzheng Chen,&nbsp;Jiawen Chen,&nbsp;Dong Wei,&nbsp;Liuyuan Li,&nbsp;Jun Cui,&nbsp;Jinbin Cao","doi":"10.1029/2025JA034029","DOIUrl":"10.1029/2025JA034029","url":null,"abstract":"<p>Electron cyclotron harmonic (ECH) waves, which are electrostatic emissions outside the plasmasphere, are of great interest because of their essential role in producing diffuse auroras. Since they are commonly observed in the first band, the global distributions of those waves in higher bands remain unknown in the magnetosphere. Using Magnetospheric Multiscale satellite data, we present the global occurrence morphology of higher band ECH waves in the magnetosphere. Higher band ECH waves are widespread in the pre-midnight to post-noon magnetosphere with occurrence rates slightly lower and spatial distribution narrower than the first band. They predominantly occur near the magnetic equator at <i>L</i> = 4–9 on the nightside but are more prevalent and extend to the duskside at high latitudes at <i>L</i> = 9–12 on the dayside. As the geomagnetic activity intensifies, their occurrence rates show an increasing tendency and their spatial coverage expands radially and azimuthally. Our results potentially contribute to understanding the magnetospheric electron dynamics driven by ECH waves.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144998710","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":"Impacts of Resolved Gravity Waves on Global-Scale Wave Variability in the Ionosphere-Thermosphere: Insights From WACCM-X, ICON, and COSMIC-2","authors":"Federico Gasperini,&nbsp;Hanli Liu","doi":"10.1029/2025JA034251","DOIUrl":"10.1029/2025JA034251","url":null,"abstract":"<p>Accurately representing the generation and evolution of global-scale wave structures in the ionosphere-thermosphere (IT) system remains a central challenge for whole-atmosphere models. The IT region exhibits substantial day-to-day variability driven by external forcing and internally generated waves. Among the most prominent internal drivers are non-migrating tides and ultra-fast Kelvin waves (UFKWs), which modulate electrodynamics and plasma distributions via wave-driven neutral winds. This study evaluates a high-resolution configuration of the Whole Atmosphere Community Climate Model with thermosphere-ionosphere extension (HR-WACCM-X) in simulating global-scale waves during September 2021, a period of enhanced vertical coupling and quiet geomagnetic conditions. Focusing on the eastward diurnal tide with zonal wavenumber 3 (DE3) and the <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>3-day UFKW, we show that HR-WACCM-X captures more realistic amplitudes, vertical structures, latitudinal extent, and variability than coarse-resolution runs. The HR simulation reproduces observed DE3 and UFKW signals in equatorial thermospheric winds and associated electron density perturbations, with correlation coefficients of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>r</mi>\u0000 <mo>=</mo>\u0000 <mn>0.43</mn>\u0000 </mrow>\u0000 <annotation> $r=0.43$</annotation>\u0000 </semantics></math>–0.63 in agreement with ICON/MIGHTI and COSMIC-2/GIS observations. Improved vertical propagation and in situ wave generation above <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>200 km yield enhanced spectral fidelity and spatial coherence in the thermospheric response. In contrast, coarse-resolution simulations underestimate amplitudes and miss key spectral features, reflecting limitations from nudging and parameterized gravity wave schemes. These results underscore the importance of resolving small-scale gravity waves to capture multiscale variability and electrodynamic coupling. The findings support the use of high-resolution whole-atmosphere models for advancing understanding of vertical coupling and wave-driven IT dynamics and provide a benchmark for future observational missions and space weather modeling.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144998711","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":"Dayside Reconnection and Associated Cusp Structure in Response to Solar Wind Rotational Discontinuity (RD) in ANGIE3D Simulation","authors":"Xiaolei Li,&nbsp;Xueyi Wang,&nbsp;Yu Lin,&nbsp;Chih-Ping Wang,&nbsp;Simon Wing,&nbsp;Gonzalo Cucho-Padin,&nbsp;Huayue Chen","doi":"10.1029/2025JA033811","DOIUrl":"10.1029/2025JA033811","url":null,"abstract":"<p>Solar wind directional discontinuities, such as rotational discontinuities (RDs), significantly influence energy and transport processes in the Earth's magnetosphere. A recent observational study identified a long-lasting double cusp precipitation event associated with RD in solar wind on 10 April 2015. To understand the magnetosphere-ionosphere response to the solar wind RD, a global hybrid simulation of the magnetosphere was conducted, with solar wind conditions based on the observation event. The simulation results show significant variations in the magnetopause and cusp regions caused by the passing RD. After the RD propagates to the magnetopause, ion precipitation intensifies, and a double cusp structure at varying latitudes and longitudes forms near noon in the northern hemisphere, which is consistent with the satellite observations by Wing et al. (2023, https://doi.org/10.1029/2023gl103194). Regarding dayside magnetopause reconnection, the simulation reveals that the high-latitude reconnection process persists during the RD passing, regardless of whether the interplanetary magnetic field (IMF) with a high <i>B</i>_<i>y</i>/<i>B</i>_<i>z</i> ratio has a positive or negative <i>B</i>_<i>z</i> component, and low-latitude reconnection occurs after the RD reaches the magnetopause at noon when the IMF turns southward. By examining the ion sources along the magnetic field lines, a connection is found between the single- or double-cusp ion precipitation and the solar wind ions entering from both high-latitude and low-latitude reconnection sites. This result suggests that the double-cusp structure can be triggered by magnetic reconnection occurring at both low latitudes and high latitudes in the opposite hemispheres, associated with a large <i>B</i>_<i>y</i>/<i>B</i>_<i>z</i> ratio of the IMF around the RD.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144990650","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":"Measuring Solar Energetic Particles With a CubeSat-Scale Energetic Particle Telescope: Geant4 Based Design of the REPTile-3 Instrument","authors":"Declan O’Brien,&nbsp;Xinlin Li,&nbsp;Christina Cohen,&nbsp;Daniel N. Baker,&nbsp;Gang Li,&nbsp;Yang Mei,&nbsp;Zheng Xiang,&nbsp;Hong Zhao,&nbsp;David Brennan,&nbsp;Wesley Martin,&nbsp;Spencer Boyajian,&nbsp;Jared Cantilina,&nbsp;Evan Bauch","doi":"10.1029/2025JA033904","DOIUrl":"10.1029/2025JA033904","url":null,"abstract":"<p>Solar Energetic Particles (SEPs) are present during increased solar activity, often associated with solar flares and coronal mass ejections (CMEs). Measuring and understanding these particles is important both for fundamental solar physics knowledge as well as the determination of radiation risks in interplanetary space. Solid-state particle telescopes are a useful tool to measure these particles. The Relativistic Electron and Proton Telescope integrated little experiment-2 (REPTile-2) was a solid-state energetic particle telescope that flew onboard the Colorado Inner Radiation Belt Experiment (CIRBE) and demonstrated a capability to measure electrons from 0.25 to 6 MeV and protons from 7 to 100 MeV with high energy and time resolution. REPTile-2 operated in a low-Earth orbit (LEO) and primarily measured radiation belt particles but was also able to measure SEPs during high-latitude passes. Because of REPTile-2's solid performance and its CubeSat-scale size, weight, and power, an opportunity arose to fly a modified REPTile-2, dubbed REPTile-3, on the Emirates Mission to the Asteroid Belt (EMA). In this paper, Geometry and tracking 4 (Geant4) Monte Carlo simulations are used to motivate changes to improve REPTile-3's ability to measure SEPs. Additionally, full instrument response functions and estimated count rates are used to understand the instrument's response to SEP fluxes. REPTile-3 is shown to be able to measure 1.2–35 MeV protons with ΔE/E &lt; 9%, 35–100 MeV protons with ΔE/E &lt; 50%, 0.1–5 MeV electrons with ΔE/E &lt; 14%, 18–131 MeV helium ions with ΔE/E &lt; 7%, and 131–200 MeV helium ions with ΔE/E &lt; 50% with a 102° field of view (FOV).</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144990652","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":"Reassessing the Relationship Between Meteor Radio Afterglows and Optical Persistent Trains","authors":"L. E. Cordonnier,&nbsp;K. S. Obenberger,&nbsp;G. B. Taylor,&nbsp;J. M. Holmes,&nbsp;J. Dowell,&nbsp;D. Vida","doi":"10.1029/2025JA034327","DOIUrl":"10.1029/2025JA034327","url":null,"abstract":"<p>Meteor radio afterglows (MRAs) and optical persistent trains (PTs) are two types of long-lived phenomena which are occasionally observed following the occurrence of a meteor. Both phenomena are thought to be produced by intrinsic emission mechanisms; PTs have been associated with chemiluminescent reactions between meteoric metals and atmospheric ozone whereas MRA emission arises due to radiation emitted by processes in the meteor's plasma trail. Previous research has identified an association between these phenomena, and proposed a mechanism by which the reactions responsible for PTs could also fuel MRAs. In this work, we investigate said connection using a substantially larger catalog containing hundreds of examples of each phenomenon. Using meteor data from the Global Meteor Network (GMN), we performed a directed search in all-sky radio images obtained by the Long Wavelength Array (LWA) radio telescope to identify meteors with MRAs. The resulting catalog spanned nearly 2 years and contained a total of 2,887 meteors, with 675 MRA events and 372 PTs. Statistical analyses suggest that the connection between the two phenomena is not as strong as previously supposed. Additionally, we show that the MRA occurrence rates do not have a strong seasonal dependence, meteoroid strength dependence, or preference between meteor showers and sporadics. Interestingly, we find that a meteor's entry angle appears to play a significant role in whether an MRA is observed.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA034327","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144990651","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":"AKR Observations From All Local Times Indicate Substorm Activity","authors":"J. E. Waters,&nbsp;L. Lamy,&nbsp;J. Coxon,&nbsp;C. M. Jackman,&nbsp;C. J. Lao,&nbsp;C. Forsyth,&nbsp;A. R. Fogg","doi":"10.1029/2025JA033955","DOIUrl":"10.1029/2025JA033955","url":null,"abstract":"<p>Auroral Kilometric Radiation (AKR) is known to present emission at lower frequencies near substorm onset, corresponding to activation of higher altitude sources along auroral magnetic field lines and acting as a proxy of the vertical distribution of acceleration processes during these events. While remote observations are more difficult to relate to ionospheric activity than those made in situ due to the illumination of the instrument by multiple AKR sources, there is a question of how the association of a particular observation with substorm activity can change with observer local time (LT) and more generally whether AKR observations can track geomagnetic activity in the same way as other proxies. This study addresses these questions by computing binary contingency tables and classification statistics including the Matthews Correlation Coefficient (MCC), using automatically selected AKR observations from Wind/WAVES and substorm event lists. AKR observations made on the dusk and dawn flanks present the greatest balance between true positive and negative associations with substorm activity, where active acceleration regions due to the enhanced substorm current wedge are distinct from typical nightside activity. Observations from the dayside and L1 can also be a reliable indicator, with AKR rarely observed from this region outside of substorm activity. Our results show that observations of AKR below 70 kHz (corresponding to active source regions above <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>12,000 km at an L-shell of 7) can act as a good discriminator of substorm activity, particularly for observations from LTs near midnight.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA033955","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144929809","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":"Imaging the D-Region Ionosphere During the 2017 Total Solar Eclipse Using VLF Measurements","authors":"Wenchen Ma,&nbsp;Wei Xu,&nbsp;Jingyuan Feng,&nbsp;Xudong Gu,&nbsp;Shiwei Wang,&nbsp;Binbin Ni,&nbsp;Wen Cheng,&nbsp;Qingshan Wang,&nbsp;Mengyao Hu,&nbsp;Haotian Xu,&nbsp;Yudi Pan","doi":"10.1029/2025JA033907","DOIUrl":"10.1029/2025JA033907","url":null,"abstract":"<p>The very-low-frequency (VLF) technique has been traditionally utilized to remotely sense the <i>D</i>-region ionosphere, but mostly for the average condition along the transmitter-receiver path, which is insufficient for atmospheric and space weather studies. The Kalman filter has thus been utilized to infer the <i>D</i>-region ionosphere over large areas. However, the inversion of <i>D</i>-region ionosphere using VLF measurements is highly nonlinear, and the Kalman filter is not suitable for this problem. Therefore, we have recently developed a method to image the <i>D</i>-region ionosphere using a particle filter and VLF measurements from a network of receivers. In this study, we verify this method using the VLF measurements during the solar eclipse that occurred at 16:48-20:01 UT on 21 August 2017 and present, for the first time, 2-D images of <i>D</i>-region ionosphere over the continental United States during this eclipse. The inversion results are highly consistent with previous studies and well-known facts: the variation of reflection height and electron density closely followed the movement of the umbra shadow, and recovered to the pre-eclipse conditions as the eclipse passed. The increase in reflection height was approximately 4.3 km during the solar eclipse, and the electron density had a maximum reduction of 79.4%. Moreover, the electron density of <i>D</i>-region ionosphere is also consistent with the obscuration factor in the extreme ultraviolet wavelength range. Our results have reconstructed the disturbance of <i>D</i>-region ionosphere caused by the 2017 solar eclipse. Therefore, this method is reliable and can be further utilized to image the <i>D</i>-region ionosphere with network measurements of VLF transmitter signals.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144927589","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":"An Explosive Leakage of Heavy Ions From Martian Crustal Magnetic Anomalies","authors":"Sanwei Cheng,&nbsp;Zhenpeng Su,&nbsp;Zewen Chen,&nbsp;Zhiyong Wu,&nbsp;Jing Wang,&nbsp;Zhonglei Gao,&nbsp;Yuming Wang","doi":"10.1029/2025JA034503","DOIUrl":"10.1029/2025JA034503","url":null,"abstract":"<p>Atmospheric escape processes are crucial for shaping the long-term surface habitability of terrestrial planets. A key question is how planetary magnetic fields influence atmospheric escape. On present-day Mars, there are crustal magnetic anomalies predominantly in the southern hemisphere, whose impact on the escape of ionospheric heavy ions remains under debate. Based on MAVEN observations, we propose a new candidate mechanism to explain how ionospheric heavy ions can escape from regions with strong crustal magnetic anomalies. This mechanism is triggered by reconnection between draped interplanetary and crustal magnetic fields, forming magnetic cusps with open field lines and generating plasma jets that impact the crustal anomalies. Within these anomalies, ions and electrons exhibit distinct spatial and temporal behaviors, leading to charge separation and the formation of an electrostatic potential. This potential lifts cold, heavy ions from the ionosphere along open field lines to escape altitudes. The process occurs within minutes, producing localized escape fluxes up to two orders of magnitude higher than background levels. This explosive leakage pattern may hold significance for other unmagnetized or weakly magnetized planets where magnetospheric and ionospheric boundaries converge.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144927606","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":"Statistical Analysis of Gravity Waves in the Mesopause Region Based on OI 557.7 nm Airglow Observation Over Mohe, China","authors":"Hui Huang,&nbsp;Sheng-Yang Gu,&nbsp;Yusong Qin,&nbsp;Guozhu Li,&nbsp;Zhenlin Yang,&nbsp;Yafei Wei,&nbsp;Dini Gong,&nbsp;Shuqi Niu","doi":"10.1029/2025JA033917","DOIUrl":"10.1029/2025JA033917","url":null,"abstract":"<p>This study statistically investigates gravity wave (GW) characteristics in the mesosphere over Mohe, China (53.5°N, 122.3°E), and utilizes three years of all-sky airglow imager data (2019–2021). A total of 2397 GW events and 608 ripple events were determined by OI airglow images on 262 clear nights. The statistical results indicate that the observed GW phase speeds ranged from 0 to 100 m/s, periods from 10 to 50 min, and horizontal wavelengths from 55 to 85 km. Notably, the observed periods and horizontal wavelengths in the Mohe region are significantly longer than in other same-latitude regions. In addition, the observed GWs showed a strong tendency to propagate northward in the first three seasons, while they shifted southeastward in winter. Specifically, northeastward propagation dominates in spring and summer, while northwestward propagation with a minor southeastward component prevailed in autumn. Based on the European Center for Medium-Range Weather Forecasts Reanalysis and the Specified Dynamics Whole Atmosphere Community Climate Model with thermosphere and ionosphere eXtension (SD-WACCM-X), further investigation suggests that tropospheric convection is the dominant source of the GWs in summer and autumn, and the generation of GWs is primarily driven by the jet stream systems in spring. In winter, GW may be affected by localized sources and filtering by the upper atmospheric background wind. This study provides valuable references for the GW parameterization in general circulation models in the northern China region.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144927605","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":"Dynamics of Thermal Electron Anisotropy in the Magnetotail Current Sheet During Substorm Growth Phase","authors":"M. Fraz Bashir,&nbsp;Anton Artemyev,&nbsp;Vassilis Angelopoulos","doi":"10.1029/2025JA034059","DOIUrl":"10.1029/2025JA034059","url":null,"abstract":"<p>The growth phase of the magnetospheric substorm is accompanied by the formation of a thin magnetotail current sheet, which is subsequently destroyed due to magnetic reconnection. The configuration and kinetic properties of this current sheet determine its stability and are important in the context of reconnection onset. This study focuses on the electron component of such thin current sheets. Observations in the near-Earth magnetotail show that electrons are predominantly field-aligned anisotropic. However, this anisotropy decreases as the current sheet becomes thinner. The observed isotropization cannot be explained by electron scattering, as anisotropy is provided by the subthermal electron population. We propose an adiabatic model for such isotropization based on observations from the Time History of Events and Macroscale Interactions during Substorms mission, and demonstrate that the inclusion of a self-consistent electrostatic field (current sheet polarization) can explain the decrease in electron anisotropy. Our findings highlight the importance of the role of electron temperature anisotropy and current sheet polarization in regulating the magnetotail dynamics during the substorm growth phase.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144927201","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}