Journal of Geophysical Research: Space Physics最新文献

{"title":"The Early-Phase Growth of ULF Waves in the Ion Foreshock Observed in a Hybrid-Vlasov Simulation","authors":"Kun Zhang,&nbsp;Seth Dorfman,&nbsp;Lucile Turc,&nbsp;Urs Ganse,&nbsp;Chen Shi,&nbsp;Hongyang Zhou,&nbsp;Minna Palmroth","doi":"10.1029/2025JA033848","DOIUrl":"https://doi.org/10.1029/2025JA033848","url":null,"abstract":"<p>Large-amplitude ultra-low frequency (ULF) waves in Earth's ion foreshock play a crucial role in the dayside dynamics and solar wind-magnetosphere coupling. This study uses global hybrid-Vlasov simulation results from Vlasiator to investigate the detailed physical processes in the early growth phase of the foreshock ULF waves. Using both spatial and temporal information, the wave phase speed is determined and used to track a specific phase front as the wave evolves. The space-time evolution of the foreshock waves and the backstreaming ions responsible for the wave growth is analyzed and presented in the wave frame for the first time. We employ a state-of-the-art linear dispersion solver, LEOPARD, to solve the wave dispersion relations using the ion distributions and compare the theoretical predictions with the measured wave phase speed and growth rate. The measured phase speed in the spacecraft (or stationary) frame is unexpectedly high at the initial growth stage but later decreases to the predicted level and exhibits an increasing trend over time that aligns with theoretical expectations. The measured and predicted growth rates share the same decreasing trend over time, but the predicted values are consistently lower than the measured growth rate by <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>25%. The comparison suggests that the foreshock waves in the Vlasiator simulation are likely generated through the ion-ion right-hand resonant instability, but there are discrepancies with linear theory that are not explained yet and require further investigation.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 7","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144511167","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":"Predictions for the Shape and Orientation of Earth's Foreshock Radiation Sources","authors":"Iver H. Cairns,&nbsp;Patrick Oppel","doi":"10.1029/2025JA033774","DOIUrl":"https://doi.org/10.1029/2025JA033774","url":null,"abstract":"&lt;p&gt;Radio emission produced in Earth's foreshock is due to the bow shock reflecting some electrons back upstream into the foreshock, where they produce Langmuir waves and radio emissions near the electron plasma frequency &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;f&lt;/mi&gt;\u0000 &lt;mi&gt;p&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${f}_{p}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; and near &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;f&lt;/mi&gt;\u0000 &lt;mi&gt;p&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $2{f}_{p}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;. Here we predict the source shapes and fluxes of Earth's foreshock radio emissions, with associated implications for other radio sources at multiples of &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;f&lt;/mi&gt;\u0000 &lt;mi&gt;p&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${f}_{p}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;. We use an extended model for Earth's foreshock radiation to calculate the electron distributions and the energy flows into Langmuir waves and radiation for specific emission processes. One extension is the addition of linear mode conversion of Langmuir waves into &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;f&lt;/mi&gt;\u0000 &lt;mi&gt;p&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${f}_{p}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; radiation at density gradients, found to produce &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;mn&gt;20&lt;/mn&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;mn&gt;30&lt;/mn&gt;\u0000 &lt;mi&gt;%&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${approx} 20-30%$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; of the total radio flux near &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;f&lt;/mi&gt;\u0000 &lt;mi&gt;p&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${f}_{p}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;. We produce the first 2D images of Earth's foreshock radio sources for &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;f&lt;/mi&gt;\u0000 &lt;mi&gt;p&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 ","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 7","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA033774","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144511238","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":"Effects of Magnetic Shear and Flow Shear on Magnetopause Magnetic Reconnection: Simultaneous Observations From MMS and THEMIS","authors":"Chongle Zhang,&nbsp;Binbin Tang,&nbsp;Wenya Li,&nbsp;Longlong Sang,&nbsp;Huijie Liu,&nbsp;Tongkuai Li,&nbsp;Jiuqi Ma,&nbsp;Wenlong Guo,&nbsp;San Lu,&nbsp;Quanming Lu,&nbsp;Chi Wang","doi":"10.1029/2025JA033778","DOIUrl":"https://doi.org/10.1029/2025JA033778","url":null,"abstract":"<p>Magnetic shear and flow shear form across Earth's magnetopause when shocked solar winds flow around Earth. Previous studies have shown that these two kinds of shears can similarly affect magnetopause reconnection. However, a direct investigation to evaluate their relative importance is lacking. In this study, we focus on simultaneous magnetopause reconnection observed by Magnetospheric Multiscale mission and Time History of Events and Macroscale Interactions during Substorms spacecraft at different magnetopause locations to quantitatively evaluate the magnetic shear and flow shear effects. The overall effect of magnetic shear (the normalized guide field &lt; 1) is limited unless the guide field is sufficient strong to suppress reconnection, whereas the flow shear can significantly affect the observed reconnection outflow speed primarily by introducing non-zero X-line motion. Finally, we propose a novel relationship combining magnetic and flow shear effects by assuming independent X-line drift motion from these two effects, which shows that the X-line drift speed is dominated by the magnetosheath flow, and the suppression of reconnection is more likely to occur under strong guide field conditions. This study deepens our understanding on magnetopause reconnection occurrence and reconnection behaviors in large scales.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 7","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144492825","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":"Asymmetric Ionospheric Disturbances Observed by GNSS During the 2017 Typhoon Talim and Doksuri: Origin and Characteristics","authors":"Junxian Fu,&nbsp;Yuichi Otsuka,&nbsp;Hidekatsu Jin","doi":"10.1029/2025JA033854","DOIUrl":"https://doi.org/10.1029/2025JA033854","url":null,"abstract":"<p>The influence of typhoons on the ionosphere has been mentioned in many studies, while the relationship and coupling processes remain elusive. Here, we report findings on concentric ionospheric disturbance (CIDs) during typhoon Talim and Doksuri, using the total electron content (TEC) data derived from the Global Navigation Satellite System (GNSS) network in Taiwan. A fourth-order Butterworth bandpass filter of 8–20 min is applied to the vertical TEC obtained for each pair of satellite and receiver to obtain the perturbation component of TEC. The CIDs were observed with a period of approximately 12 min and a horizontal phase velocity of 141–163 m/s. The CIDs are related to the atmospheric gravity waves (AGWs) generated by upward-moving air in the intense convective regions prompted by typhoons. A pattern of east-west asymmetry, that the TEC variations were significantly more pronounced in the direction opposing the background wind (eastward) compared to the direction aligned with it (westward), was observed in the CIDs. Besides, a model calculation of the electron density variation related to AGWs is used in this study. By the GAIA model, the background wind direction is generally west-northwest. This asymmetry pattern is thought to be the effect of background winds on the vertical wavelength of gravity waves, leading to differences in ionospheric electron density variations in the different directions of gravity wave propagation. The results of model calculations are consistent with the TEC variations from GNSS observations.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 7","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA033854","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144492817","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":"Responses of the Ionospheric Zonal Currents From Equator to Middle Latitudes During the Intense Geomagnetic Storm on 10–12 May 2024","authors":"Chao Xiong,&nbsp;Yuyang Huang,&nbsp;Fengjue Wang,&nbsp;Hermann Lühr,&nbsp;Yunliang Zhou,&nbsp;Jia Zhu","doi":"10.1029/2025JA033992","DOIUrl":"https://doi.org/10.1029/2025JA033992","url":null,"abstract":"<p>In this study, we performed a detailed analysis of the ionospheric zonal currents from equator to middle latitudes during the recent intense geomagnetic storm on 10–12 May 2024. Magnetic measurements from two ground stations in the America sector as well as those from the Swarm satellites have been used. Extreme intensified eastward and westward EEJ values reaching 300 and −400 mA/m have been observed during the storm main and recovery phases, respectively. Such intense EEJ values have never been observed during the past 11-year flying period of Swarm mission. In addition, the storm responses of zonal currents at low and middle latitudes have been analyzed using the vertical magnetic field component from Swarm. These zonal currents showed quite prominent dependence on magnetic local time. In the noon sector, eastward currents were dominated under both quiet and storm conditions, with slight intensification during the storm. Conversely, the zonal currents in the dawn and dusk sectors displayed abrupt current reversals within 30 min after the storm sudden commencement, characterized by sustained eastward (dawn) and westward (dusk) perturbations persisting for the rest of one and a half days. Most interestingly, two eastward zonal current jets were found located at ±25° magnetic latitudes at the dusk sector and emerged with westward zonal currents at other low and middle latitudes. We speculate that a shear layer of zonal eastward winds is needed at a conjugate altitude to cause the narrow eastward current jets. To our knowledge, this is the first report of such narrow current jets at middle latitudes during storms.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 7","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144492862","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":"Investigation of Daytime Electromagnetic Power in the Topside Ionosphere Radiated From VLF Transmitters During Solar Minimum Period of Cycle 23/24","authors":"Shengyang Huang,&nbsp;Shufan Zhao,&nbsp;Li Liao,&nbsp;Xuan Dong,&nbsp;Hengxin Lu,&nbsp;Xuhui Shen","doi":"10.1029/2025JA033950","DOIUrl":"https://doi.org/10.1029/2025JA033950","url":null,"abstract":"<p>The propagation of Very Low Frequency (VLF) waves from ground-based VLF transmitters worldwide allows them to penetrate the ionosphere and enter the magnetosphere. This interaction drives electron precipitation in the inner radiation belts through resonant interactions. The energy loss of VLF waves penetrating the ionosphere occurs mainly in the lower ionosphere, which is mainly affected by solar shortwave radiation. However, the solar activity affecting the energy of VLF transmitter signals reaching the topside ionosphere has not been sufficiently studied during the solar minimum period. In this paper, we quantify the correlation between the electromagnetic field radiated to the topside ionosphere by different VLF transmitters and solar activity, as well as the energy injected into the topside ionosphere during the daytime, using data from the DEMETER satellite. Our findings demonstrate that both the average daytime radiated electric field and magnetic field above the four VLF transmitters are negatively correlated with solar activity. Furthermore, even during the lower solar activity years, the radiated power in the topside ionosphere from VLF transmitters in the winter of 2008 during the daytime was found to be more than 2.5 times higher than that in the winter of 2004.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144367214","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":"MHD Simulations of Europa's Interaction With Jupiter's Magnetosphere During the Juno Flyby: Electron Beams in the Plasma Wake","authors":"S. Cervantes,&nbsp;J. Saur,&nbsp;S. Duling,&nbsp;J. R. Szalay,&nbsp;S. Schlegel,&nbsp;J. E. P. Connerney,&nbsp;F. Allegrini,&nbsp;S. Bolton","doi":"10.1029/2025JA033825","DOIUrl":"https://doi.org/10.1029/2025JA033825","url":null,"abstract":"<p>In September 2022, the Juno mission performed its only close flyby of Europa and traversed the moon's wake at a minimum distance of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>350 km. Among other findings, the Jovian Auroral Distributions Experiment (JADE) detector onboard the spacecraft discovered intense field-aligned electron beams (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>30–300 eV) downstream of the moon. In this study, we apply a three-dimensional magnetohydrodynamic model to simulate the plasma interaction of Jupiter's magnetosphere with Europa and its atmosphere for the conditions of this flyby, and we specifically focus on the influence of the electron beams on the plasma density and the magnetic field in the moon's space environment. We include these beams in our simulations as sheets of locally enhanced ionization, and we use electron impact ionization rates of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>O</mi>\u0000 <mn>2</mn>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${mathrm{O}}_{mathrm{2}}$</annotation>\u0000 </semantics></math> derived from JADE electron measurements to characterize the sheets. We compare our results with the magnetic field and the total ion number density measurements from Juno's magnetometer and JADE detector, respectively. Our results show that the beams fill the wake downstream of Europa with newly ionized plasma, and that they generate large variations in the magnetic field which contribute partially to the observed magnetic field. Our study demonstrates that the electron beams are critical factors in shaping Europa's magnetic field and plasma environment, and thus they need to be accounted for in the data analysis of the upcoming JUICE and Europa Clipper missions.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA033825","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144367217","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":"Investigating Rotation and Anisotropic Ablation of Small Meteoroids and Their Effects on Head Echo Plasma Formation via Computational Techniques","authors":"T. Hedges,&nbsp;J. C. Ferguson,&nbsp;N. Lee,&nbsp;S. Elschot,&nbsp;G. Sugar,&nbsp;M. M. Oppenheim","doi":"10.1029/2025JA033883","DOIUrl":"https://doi.org/10.1029/2025JA033883","url":null,"abstract":"<p>High-power large-aperture radar instruments observe numerous meteor head echoes per minute. Head echoes result from reflections of radio waves from plasma surrounding meteoroids as they enter Earth's atmosphere. Knowledge of the spatial distribution of electrons in this plasma is essential to determining the mass loss rate of the meteor as a function of its measured radar cross-section. Prior work applies theoretical and computational methods to determine the electron density distribution, but assumes the meteoroid emits neutral particles uniformly across its surface. In this paper, a numerical surface ablation model demonstrates that meteoroid mass loss may occur preferentially in the direction facing the oncoming atmosphere. Specifically, meteoroid mass loss becomes proportional to the frontal surface area facing the freestream atmosphere in the limit of high Biot number, but remains isotropic in the limit of low Biot number. Meteoroid rotation has a small effect on the direction of ejected mass, but the effect is insignificant compared to variation in meteoroid properties that affect the Biot number. This result informs our computational meteor plasma model, in which we compare the effect of meteoroid vaporization on the plasma distribution in the limits of low versus high Biot number. The resulting electron density profiles demonstrate order-of-magnitude agreement between each other, with peak difference of 70% immediately upstream of the meteoroid. This implies that the directional distribution of vaporizing neutrals likely does not significantly influence head echo observations, lending credence to existing work that assumes isotropic ablation.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144367216","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":"Lidar Observations of Thermosphere-Ionospheric Ca+ at Mohe (122.3°E, 53.5°N)","authors":"Jing Jiao,&nbsp;Fang Wu,&nbsp;Lifang Du,&nbsp;Guotao Yang,&nbsp;Haoran Zheng,&nbsp;Xiaofei Wu","doi":"10.1029/2025JA033813","DOIUrl":"https://doi.org/10.1029/2025JA033813","url":null,"abstract":"<p>The ionosphere is an open area, affected by solar activity or geomagnetic activity, and affected by the lower atmosphere. Moreover, previous studies believed that metallic iron ions were a necessary condition for the formation of ionospheric irregularities, but so far there are no favorable observations to support it. In this paper, we use a Ca⁺ lidar at Mohe to explore the relationship between metal ions and ionospheric irregularities. The reason for choosing Mohe Station is that this region is at the northernmost point of China and is on the edge of the sub-aurora zone during the peak year of solar activity. Mohe thermosphere and ionosphere Ca⁺ (TICa⁺) is associated with Spread F or may be related with magnetic storms. The TICa⁺ generally occurred before dawn. In addition, the density of main Ca⁺ layer (80–120 km) in the autumn months is low, and the upper TICa⁺ (120–300 km) event density is also low with an order of 10 cm⁻³. However, during magnetic storm periods, the density of TICa⁺ increased with an order of 100 cm⁻³, which is comparable to or higher than summer results.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144339599","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":"Spatial Distribution and Geomagnetic Dependence of Radiation Belt Electron Reversed Energy Spectrum","authors":"Jiaming Li,&nbsp;Yuequn Lou,&nbsp;Xudong Gu,&nbsp;Binbin Ni,&nbsp;Qi Zhu,&nbsp;Xin Ma,&nbsp;Shuqin Chen","doi":"10.1029/2025JA033738","DOIUrl":"https://doi.org/10.1029/2025JA033738","url":null,"abstract":"<p>Using high-quality electron measurements from Van Allen Probes during October 2013 and March 2019, this study investigates the spatial distribution and geomagnetic dependence of the electron reversed energy spectrum in the Earth's radiation belts. The reversed energy spectrum is primarily observed within the L-shell range of ∼2.6–5.2, with peak occurrence rates reaching ∼50% at <i>L</i> = ∼4. Occurrence rates are higher in the post-noon to midnight sectors and lower on the pre-dawn side. In terms of magnetic latitude (MLAT), the spectrum spans ∼−20°–20°, exhibiting south-north asymmetry, particularly in the noon and night regions. The characteristic energies defining the spectrum correspond to the flux minimum (Ev) and maximum (Ep), which typically range from ∼100 keV to ∼1 MeV and hundreds of keV–∼2 MeV, respectively, with both Ev and Ep decreasing as <i>L</i> increases. The spectrum is more frequently observed during geomagnetically quiet periods, with maximum occurrence rates exceeding 50%. However, as geomagnetic activity intensifies, the occurrence rates decrease significantly, and the favorable region contracts toward lower L-shells. Analysis of geomagnetic indices shows that the reversed energy spectrum is more strongly affected by the Dst index than the auroral electrojet (AE) index. This could suggest a more substantial influence of geomagnetic storms than the substorm activity on suppressing the electron reversed energy spectrum. These results improve our understanding of how radiation belt electron dynamics respond to geomagnetic disturbances, emphasizing the interplay between storms, substorms, and wave-particle interactions in shaping the evolution of the reversed electron energy spectrum.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144339372","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}