Journal of Geophysical Research: Space Physics最新文献

{"title":"Automated Identification of Auroral Luminosity Boundaries Using pyIntensityFeatures","authors":"Angeline G. Burrell,&nbsp;Gareth Chisham,&nbsp;Nicola Longden,&nbsp;Bruce Fritz,&nbsp;Kate A. Zawdie","doi":"10.1029/2025JA034230","DOIUrl":"10.1029/2025JA034230","url":null,"abstract":"<p>Imagers that observe optical or ultraviolet emissions from the atmosphere are commonly used to identify and study ionospheric phenomena. These phenomena include the auroral oval, equatorial plasma bubbles, and traveling ionospheric disturbances. One difficulty with using imager observations is accurately and automatically retrieving locations of interest from these images. This article presents an automated method designed to identify auroral luminosity boundaries from space-based imager data. This method was originally developed for the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) observations, but has been further adapted for use with a wider range of observations. This article discusses the updated boundary detection method, and demonstrates the process on two different satellite data sets. The updated detection method has been made publicly accessible through a new Python package, <i>pyIntensityFeatures</i>.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145146363","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":"The NCAR-TIEGCM Version 3.0","authors":"Haonan Wu,&nbsp;Wenbin Wang,&nbsp;Kevin H. Pham,&nbsp;Dong Lin,&nbsp;Nikhil Rao,&nbsp;Michael J. Wiltberger,&nbsp;Gang Lu,&nbsp;Qian Wu,&nbsp;Hanli Liu,&nbsp;Liying Qian,&nbsp;Chih-Ting Hsu,&nbsp;Nicholas M. Pedatella,&nbsp;Jordi Vila-Pérez,&nbsp;Joseph M. McInerney,&nbsp;Arthur D. Richmond,&nbsp;Alan G. Burns,&nbsp;Stanley C. Solomon,&nbsp;Astrid Maute,&nbsp;Eric K. Sutton,&nbsp;Xian Lu,&nbsp;Xuguang Cai,&nbsp;Cheng Sheng,&nbsp;Jack C. Wang,&nbsp;Jia Yue","doi":"10.1029/2025JA034219","DOIUrl":"10.1029/2025JA034219","url":null,"abstract":"<p>A new version of the US National Science Foundation National Center for Atmospheric Research (NSF NCAR) thermosphere-ionosphere-electrodynamics general circulation model (TIEGCM) has been developed and released. This paper describes the changes and improvements of the new version (3.0) since its last major release (2.0) in 2016. These include: (a) increasing the model resolution in both the horizontal and vertical dimensions, as well as in the ionospheric dynamo solver; (b) upward extension of the model upper boundary to enable more accurate simulations of the topside ionosphere and neutral density in the lower exosphere; (c) improved parameterization for thermal electron heating rate; (d) resolving transport of minor species N(²D); (e) treating helium as a major species; (f) parameterization for additional physical processes, such as SAPS and electrojet turbulent heating; (g) including parallel ion drag in the neutral momentum equation; (h) nudging of prognostic fields near the lower boundary from external data; (i) modification to the NO reaction rate and auroral heating rate; (j) outputs of diagnostic analysis terms of the equations; (k) new functionalities enabling model simulations of certain recurrent phenomena, such as solar flares and eclipses. We present examples of the model validation during a moderate storm and compare simulation results by turning on/off new functionalities to demonstrate the related new model capabilities. Furthermore, the model was upgraded to comply with the new computer software environment at NSF NCAR for easy installation and run setup and with new visualization tools. Finally, the model limitations and future development plans are discussed.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA034219","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145146426","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":"Observations of Kelvin-Helmholtz Waves on Mercury's Pre-Dawnside Magnetopause: MESSENGER Case Study","authors":"Ruotan Li,&nbsp;Weijie Sun,&nbsp;Suiyan Fu,&nbsp;Ryan M. Dewey,&nbsp;Jiutong Zhao,&nbsp;Caitriona M. Jackman,&nbsp;James A. Slavin,&nbsp;Gang Kai Poh,&nbsp;Jim M. Raines,&nbsp;San Lu,&nbsp;Jin Guo,&nbsp;Zhekai Luo,&nbsp;Zuyin Pu,&nbsp;Lun Xie","doi":"10.1029/2025JA033828","DOIUrl":"10.1029/2025JA033828","url":null,"abstract":"<p>Kelvin-Helmholtz (K-H) waves are important in transporting mass, momentum, and energy across magnetic boundaries in space plasma. This study presents the observations of K-H waves on Mercury's pre-dawnside magnetopause, where more than 10 linear and non-linear K-H waveforms were identified. Adjacent to these waves, compressional ultra-low frequency waves and ion-Bernstein modes along with a proton distribution exhibiting a positive phase space density gradient were observed. These observations suggest that energy and mass are transported by the K-H waves. However, during the same MESSENGER's orbit on the pre-duskside magnetopause, only a few magnetopause oscillations were observed and there is no accompanied compressional waves and ion-Bernstein modes. The differences might be attributed to that MESSENGER crossed the dusk magnetopause on the dayside, where K-H waves may not have fully developed. Another possible reason might be due to the direction of the interplanetary magnetic field. When the quasi-parallel bow shock is located on the dawnside, it generates a smaller tangential magnetic field in the magnetosheath, which allows K-H waves to be more easily excited. Our findings provide new insights into occurrences and energy transport of K-H waves in Mercury's magnetosphere.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145129356","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":"Trunk-Like Ion Spectral Structures: Manifestation of Azimuthal Ion Dispersion in the Inner Magnetosphere","authors":"Fan Yang,&nbsp;Xu-Zhi Zhou,&nbsp;Ye Jin,&nbsp;Ya-Ze Wu,&nbsp;Jie Ren,&nbsp;Jianyong Lu,&nbsp;Chao Yue,&nbsp;Yong-Yong Feng,&nbsp;Qiu-Gang Zong","doi":"10.1029/2025JA034504","DOIUrl":"10.1029/2025JA034504","url":null,"abstract":"<p>In the Earth's inner magnetosphere, the complex interplay of ion transport, acceleration, and loss processes often manifests in spacecraft observations as distinct ion spectral structures. An intriguing type of such structures, the trunk-like structures named for their resemblance to elephant trunks in the energy-time spectrograms of heavy ions below several keV, is characterized by enhanced fluxes at progressively lower energies toward Earth. An outstanding puzzle from Van Allen Probes observations is that these structures appear predominantly during inbound, rather than outbound, spacecraft passes. This strong inbound-outbound asymmetry indicates that the ions in the trunk-like structures are not dispersed solely in the radial direction; azimuthal dispersion must also be involved. We show that such dispersion arises naturally from the energy-dependent gradient-curvature drift motion of the ions following their sudden injection into the inner magnetosphere. Despite its simplicity, this mechanism captures the essential signatures of many observed trunk-like structures, although additional processes may still contribute. Moreover, the same azimuthal dispersion mechanism may also account for the formation of multiple nose-like structures observed during the outbound passes. These findings highlight how a seemingly complicated observational puzzle can be resolved with a straightforward physical explanation, enhancing our understanding of particle dynamics in the inner magnetosphere.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145129351","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":"High Latitude EMIC Waves in the Earth's Inner Magnetosphere: A Global View of the Wave-Induced Source for Heavy Ion Conics and Warm Plasma Cloak","authors":"Konstantin V. Gamayunov,&nbsp;Hyomin Kim,&nbsp;Youra Shin","doi":"10.1029/2025JA034105","DOIUrl":"10.1029/2025JA034105","url":null,"abstract":"&lt;p&gt;This study is a follow-up to the Gamayunov et al. (2024, https://doi.org/10.1029/2023ja032399) paper, where they show that dissipation of the &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;H&lt;/mi&gt;\u0000 &lt;mi&gt;e&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;mo&gt;+&lt;/mo&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{H}mathrm{e}}^{+}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;-band and &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;H&lt;/mi&gt;\u0000 &lt;mo&gt;+&lt;/mo&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{H}}^{+}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;-band electromagnetic ion cyclotron (EMIC) wave energy in the postnoon magnetic local time (MLT) off equatorial region of the Earth's inner magnetosphere substantially contributes to the formation of heavy ion conics and warm plasma cloak. Here, we extend the scope of their paper by providing a global view of the EMIC wave-induced source for heavy ion conics and warm plasma cloak in the inner magnetosphere. We produce a database of the &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;H&lt;/mi&gt;\u0000 &lt;mi&gt;e&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;mo&gt;+&lt;/mo&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{H}mathrm{e}}^{+}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;-band and &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;H&lt;/mi&gt;\u0000 &lt;mo&gt;+&lt;/mo&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{H}}^{+}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;-band EMIC wave events using observations by the two Van Allen Probes in the magnetic latitude region &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;mi&gt;M&lt;/mi&gt;\u0000 &lt;mi&gt;L&lt;/mi&gt;\u0000 &lt;mi&gt;A&lt;/mi&gt;\u0000 &lt;mi&gt;T&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/mfenced&gt;\u0000 &lt;mo&gt;≥&lt;/mo&gt;\u0000 &lt;mn&gt;10&lt;/mn&gt;\u0000 &lt;mo&gt;°&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $leftvert mathrm{M}mathrm{L}mathrm{A}mathrm{T}rightvert ge 10{}^{circ}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; from the beginning through the end of mission and then analyze it. The major results of our analysis are as follows. (a) About two thirds of EMIC wave events a","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA034105","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145129299","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":"Formation Mechanism and Interhemispheric Asymmetry of Storm-Enhanced Density During April 2023 Storm Revealed by GITM","authors":"Yulu Peng,&nbsp;Shasha Zou,&nbsp;Zihan Wang,&nbsp;Xiantong Wang,&nbsp;Aaron Ridley,&nbsp;Grace Kwon,&nbsp;Mary Smirnova","doi":"10.1029/2025JA034034","DOIUrl":"10.1029/2025JA034034","url":null,"abstract":"<p>We investigate the formation and interhemispheric asymmetries of storm-enhanced density (SED) during the April 23–24, 2023 geomagnetic storm using the Global Ionosphere-Thermosphere Model (GITM) coupled with high-latitude drivers from the Geospace model. This storm, driven by an interplanetary coronal mass ejection (ICME), featured two southward IMF intervals—the ICME sheath followed by a magnetic cloud (MC)—each producing SED with distinct asymmetries. During the sheath phase, SEDs formed in both hemispheres with a stronger isolated peak in the south. During the MC phase, a weaker SED appeared only in the north, despite a stronger IMF B_z. GITM results indicate that equatorward neutral wind-induced upward ion drift was the primary driver of midlatitude SEDs, while convection electric fields dominated high-latitude SED and plume lifting. Differences in SED response between the two phases highlight the role of thermospheric composition and its temporal history in shaping storm-time ionospheric density, including pre-storm modulation, storm-time reinforcement, and interhemispheric asymmetry of magnetic poles with universal time (UT) effect. The prominent southern SED during the sheath phase was attributed to a higher O/N2 ratio from preconditioning and storm-time reinforcement, whereas the expanded convection during the MC phase lowered O/N2 in southern midlatitudes and limited SED growth. The impacts of large-scale traveling atmospheric/ionospheric disturbances (TADs/TIDs) on SED formation were minimal. This study quantifies various factors driving SED formation and highlights the sustained impact of ICME sheath during a double-dip storm on ionosphere-thermosphere dynamics and the role of thermospheric composition in modulating SED location, characteristics, and hemispheric asymmetry.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA034034","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145110792","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":"Geomagnetic Activity Dependence of the Auroral Electron Precipitation Spectrum at High Latitudes","authors":"S. Oyama,&nbsp;I. I. Virtanen,&nbsp;H. W. Tesfaw,&nbsp;T. Raita,&nbsp;L. Holappa,&nbsp;Y. Miyoshi,&nbsp;L. Cai,&nbsp;H. Vanhamäki,&nbsp;A. T. Aikio,&nbsp;Y. Ogawa,&nbsp;K. Hosokawa","doi":"10.1029/2024JA033441","DOIUrl":"10.1029/2024JA033441","url":null,"abstract":"<p>Auroral electron forcing with energy greater than tens keVs impacts D-region ionization in high-latitude regions, exhibiting increased energy from midnight to dawn. This increase, known as spectrum hardening, is characterized by a higher energy at the electron-precipitation peak flux and/or a gradual power-law spectrum gradient. The former relates to the Maxwellian component of the spectrum, while the latter pertains to the Kappa distribution component. However, limited research has distinguished these two components. This study investigated the dependence of the D-region ionization on geomagnetic activity using electron density data from the European Incoherent Scatter (EISCAT) radar in Norway and cosmic noise absorption in Finland, sorted by the SuperMAG Auroral Electrojet index (SME). An inversion method derived differential energy spectra from the EISCAT-measured height-resolved electron density. Statistical spectrum analysis by fitting the Kappa distribution function revealed that spectrum hardening from midnight to dawn at auroral latitudes is mainly driven by the Kappa distribution component, characterized by a gradual power-law spectrum gradient for moderately high geomagnetic activities (SME ≥300 nT). Conversely, for SME &lt;300 nT, the Maxwellian component primarily also contributes to spectrum hardening. This study is the first to specify the energy range contributing to spectrum hardening.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA033441","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145110791","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":"Mechanism for Sporadic E Enhancement During the May 2024 Geomagnetic Storm: TIEGCM Simulation","authors":"Lihui Qiu,&nbsp;Huixin Liu,&nbsp;Tingting Yu","doi":"10.1029/2025JA034455","DOIUrl":"10.1029/2025JA034455","url":null,"abstract":"<p>Based on 37 ground-based ionosondes and space-based COSMIC-2 radio occultation observations, Qiu and Liu (2025, https://doi.org/10.1029/2025gl115154) recently reported that Es layers were significantly enhanced during the May 2024 super geomagnetic storm. To explain these observations, this study investigates the geographical distribution and temporal evolution of vertical ion convergence (VIC) that is calculated from the neutral winds simulated by the Thermosphere-Ionosphere-Electrodynamics General Circulation Model. The results show that the VIC was significantly enhanced over East Asia-Australia and Pacific sectors within the 40°S–40°N latitude band, and the VIC patterns exhibit a clear “equatorward propagation” feature, which agrees well with previously observed Es layer intensification patterns. By comparing the contributions of zonal and meridional winds to the VIC enhancement, the result shows that the VIC enhancement is primarily driven by the strengthening of westward winds in this event. These studies suggest that the impacts of super geomagnetic storms on the solar-terrestrial environment can extend to the mesosphere and lower thermosphere and affect the behaviors of irregularities in the ionospheric <i>E</i> region.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA034455","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145110919","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":"Medium Scale Traveling Ionospheric Disturbances Observed by the SuperDARN Radars Located in the Asian Mid-Latitude","authors":"Hang Li,&nbsp;Jiaojiao Zhang,&nbsp;Wei Wang,&nbsp;Longchang Sun,&nbsp;Jiyao Xu,&nbsp;Xiang Deng,&nbsp;Ailan Lan,&nbsp;Jingye Yan,&nbsp;Nozomu Nishitani,&nbsp;Chi Wang","doi":"10.1029/2025JA033978","DOIUrl":"10.1029/2025JA033978","url":null,"abstract":"&lt;p&gt;Medium-scale traveling ionospheric disturbances (MSTIDs) manifest as quasi-periodic enhancements and depletions in ionospheric electron density, primarily caused by ion-neutral collisions, plasma instabilities, and electromagnetic forcing. Super Dual Auroral Radar Network (SuperDARN) radars are powerful instruments that can be used to study the ionospheric irregularities, MSTIDs, and many other phenomena. Newly built SuperDARN radars were deployed in the Chinese mid-latitude region (CN-DARN) to provide us with the opportunity to study the propagation and evolution of MSTIDs on a larger scale in the Asian region. In this paper, a southwestward propagation of MSTIDs in Asia was observed by two Japanese SuperDARN radars: the Hokkaido East Radar (HOK), Hokkaido West Radar (HKW), and two Chinese SuperDARN radars: Siziwang East Radar (SZE), and Siziwang West Radar (SZW), in combination with 630-nm all-sky airglow imager (ASAI) and Global Navigation Satellite System - Total Electron Content (GNSS-TEC) measurements. The dominant direction of the MSTIDs was toward the southwest at −117 &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; $pm $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; 8 to −145 &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; $pm $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; 6°. Horizontal wavelengths ranged from 321 &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; $pm $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; 37 to 462 &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; $pm $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; 36 &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;k&lt;/mi&gt;\u0000 &lt;mi&gt;m&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $mathrm{k}mathrm{m}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, periods were between 24 &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; $pm $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; 2 and 30 &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; $pm $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; 2 min, and horizontal phase velocities varied from 182 &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; $pm $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; 36 to 257 &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","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145102126","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":"Electron Acceleration by Structured Parallel Electric Field Within a Reconnecting Current Sheet in the Turbulent Magnetosheath","authors":"Shimou Wang,&nbsp;Rongsheng Wang,&nbsp;Quanming Lu,&nbsp;Kai Huang,&nbsp;San Lu,&nbsp;Yukang Shu,&nbsp;Jin Guo","doi":"10.1029/2025JA033817","DOIUrl":"10.1029/2025JA033817","url":null,"abstract":"<p>Turbulent energy dissipation and the resulting plasma heating are thought to be important in various space and astrophysical systems. In this study, we present in situ evidence of electron acceleration by a localized parallel electric field in the turbulent magnetosheath, the region downstream of the Earth's bow shock. The observed profile of the parallel electric field presents a near unipolar spike, with numbers of irregular bipolar signals superimposed. This structured parallel electric field is generated in an ion-scale reconnecting current sheet, concurrent with observations of field-aligned bidirectional electron beams, large energy dissipation, and significant electron parallel heating, indicating a link between them. The electrons are demonstrated to be trapped in this current sheet and accelerated directly by a parallel electric field. Our results reveal that flat-top electron distributions, which are commonly observed in the magnetosheath, do not have to originate from the shock acceleration but can also be generated by a localized acceleration potential. Such an acceleration potential is common in reconnecting current sheets, and its contribution to electron heating can be significant in a turbulent system populated by numerous current sheets.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145102212","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}