Journal of Geophysical Research: Space Physics最新文献

{"title":"Properties of Ion Upflows in the Low-Altitude Polar Ionosphere During CIR- and CME- Driven Magnetic Storms Based on Long-Term EISCAT Observations","authors":"M. Takada,&nbsp;K. Seki,&nbsp;Y. Ogawa,&nbsp;K. Keika","doi":"10.1029/2024JA032691","DOIUrl":"https://doi.org/10.1029/2024JA032691","url":null,"abstract":"<p>We have investigated the effects of Corotating Interaction Region- (CIR-) and Coronal Mass Ejection- (CME-) driven magnetic storms on the characteristics and mechanisms of ion upflow in the low-altitude ionosphere (250–350 km). Our analysis was based on observations from the European Incoherent Scatter (EISCAT) radars at Tromsø (ILAT = ∼66<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <annotation> $mathit{{}^{circ}}$</annotation>\u0000 </semantics></math>N) and Svalbard (∼75<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <annotation> $mathit{{}^{circ}}$</annotation>\u0000 </semantics></math>N) from 1996 to 2015. The ion upflows (defined by the averaged upward ion velocity of &gt;10 m/s) in the low-altitude ionosphere were mainly detected in the MLT sectors of 03–09 (dawnside) and 21-03 (nightside) at Tromsø during both CIR- and CME-driven magnetic storms. The ion upflows at Svalbard were not enhanced on the nightside but were remarkable on the dawnside during CIR-driven storms and were also observed on the nightside during CME-driven large storms. On the duskside (15–21 MLT), the low-altitude ion upflows were only detected at Tromsø during CME-driven large storms. Dayside (09–15 MLT) ion upflows were not detected in the low-altitude ionosphere. To investigate the generation mechanisms of low-altitude ion upflows, we compared the convection electric field, ion temperature, and electron temperature between the pre-storm time and after storm onset. The results indicate that frictional heating (Type 1 ion upflow) is dominant at Tromsø during CME-driven large storms in all MLT sectors except the dayside. Conversely, particle precipitation (Type 2 ion upflow) is dominant at Tromsø on the nightside during all magnetic storms except CME-driven large storms. Both mechanisms contribute to ion upflow during CIR-driven small storms on the dawnside of Svalbard.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 10","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA032691","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145317499","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":"Reconnection and Viscous Control of Dayside Field-Aligned Currents for Northward Interplanetary Magnetic Field","authors":"S. E. Milan,&nbsp;M. K. Mooney,&nbsp;G. E. Bower,&nbsp;G. Kennedy,&nbsp;B. J. Anderson,&nbsp;S. K. Vines,&nbsp;M. R. Hairston","doi":"10.1029/2025JA034547","DOIUrl":"https://doi.org/10.1029/2025JA034547","url":null,"abstract":"<p>We study the morphology and magnitude of dayside field-aligned currents (FACs) for northward interplanetary magnetic field (IMF) using observations from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). For near-zero IMF clock angles the FACs form a quadrupolar pattern centered at local noon, which is associated with the reverse convection cells driven by lobe reconnection. The poleward pair of FACs, known as the northward-<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>B</mi>\u0000 <mi>Z</mi>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${B}_{Z}$</annotation>\u0000 </semantics></math> or NBZ FAC system, comprises upward and downward FAC pre- and post-noon; and the equatorward pair have the opposite polarity. The magnitude of the NBZ FACs is modulated by dipole tilt and phase of the solar cycle, the former controlling the solar zenith angle in the vicinity of the FACs, and the latter controlling the solar radio flux at 10.7 cm (F10.7), both of which contribute to the conductance of the ionosphere. The NBZ FACs are also modulated by the magnitude of the IMF (or the Z-component of the IMF for near-zero clock angle), which we presume controls the lobe reconnection rate. The NBZ FACs do not respond to the X-component of the IMF, solar wind speed, nor solar wind density, so we presume that these do not affect the lobe reconnection rate. High solar wind speed leads to the appearance of region 1 and 2 FACs at auroral latitudes, which we suggest are associated with a viscous interaction between the solar wind and the magnetosphere.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 10","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA034547","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145317496","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":"Scaling of Ion Outflow Speed and Ion Bulk Heating in Lobe Reconnection and Their Relations to Shear Flow","authors":"H. Koike,&nbsp;S. Taguchi","doi":"10.1029/2025JA033783","DOIUrl":"https://doi.org/10.1029/2025JA033783","url":null,"abstract":"<p>Magnetic reconnection at the high-latitude magnetopause is accompanied by velocity shear due to the tailward flow of the magnetosheath. This study investigates 24 high-latitude magnetopause reconnection events observed by the Cluster satellites and examines how ion outflow speed and ion bulk heating depend on the upstream Alfvénic parameters and shear flow speed. We find that the ion outflow speed and ion bulk heating scale well with the hybrid asymmetric Alfvén speed (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>V</mi>\u0000 <mrow>\u0000 <mtext>A</mtext>\u0000 <mi>L</mi>\u0000 <mo>,</mo>\u0000 <mtext>asym</mtext>\u0000 </mrow>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${V}_{text{A}mathit{L},text{asym}}$</annotation>\u0000 </semantics></math>) and the inflowing magnetic energy per particle (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>m</mi>\u0000 <mi>i</mi>\u0000 </msub>\u0000 <msubsup>\u0000 <mi>V</mi>\u0000 <mrow>\u0000 <mtext>A</mtext>\u0000 <mi>L</mi>\u0000 <mo>,</mo>\u0000 <mtext>asym</mtext>\u0000 </mrow>\u0000 <mn>2</mn>\u0000 </msubsup>\u0000 </mrow>\u0000 <annotation> ${m}_{i}{V}_{text{A}mathit{L},text{asym}}^{2}$</annotation>\u0000 </semantics></math>), respectively, calculated using the upstream magnetic field and plasma density on both the magnetosheath and lobe sides. This is the first observational evidence that the Alfvénic scaling relationships, previously known for reconnection in the solar wind and at the low-latitude magnetopause, also hold true for reconnection at the high-latitude magnetopause. We also find that both the ion outflow speed and ion bulk heating show a positive correlation with shear flow speed. These results imply that as shear flow speed increases, the magnetic field and plasma density in the magnetosheath near the lobe reconnection region may adjust in a way that increases <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>V</mi>\u0000 <mrow>\u0000 <mtext>A</mtext>\u0000 <mi>L</mi>\u0000 <mo>,</mo>\u0000 <mtext>asym</mtext>\u0000 </mrow>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${V}_{text{A}mathit{L},text{asym}}$</annotation>\u0000 </semantics></math>.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 10","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA033783","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145317497","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":"Fine-Scale Structure in Plasmaspheric Plumes From GEO to the Magnetopause: Observations by Magnetospheric Multiscale","authors":"J. Goldstein,&nbsp;M. J. Kim,&nbsp;S. A. Fuselier,&nbsp;J. Mukherjee,&nbsp;C. A. Gonzalez,&nbsp;R. Gomez,&nbsp;J. L. Burch","doi":"10.1029/2025JA034042","DOIUrl":"https://doi.org/10.1029/2025JA034042","url":null,"abstract":"<p>Plasmaspheric fine-scale structure (FSS) comprises density irregularities below 0.1–0.2 Earth radii in size. In this paper, we investigate FSS within dayside plasmaspheric plumes as they convect sunward from geosynchronous orbit to the magnetopause. We perform a statistical study of Magnetospheric Multiscale ion data, analyzing 39,018 ion moments from 122 plume events. We find FSS grows inside sunward-moving dayside plumes, increasing exponentially with 8–11 hr timescale. Spatially, FSS becomes concentrated in the outer duskside region where ion drift paths converge toward the magnetopause. We also investigate basic properties of plume ions. We confirm that plume ion temperature increases with distance, and find that for most plumes light ion densities are correlated to each other. In older plumes (18% of our database) with preferential heating of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mrow>\u0000 <msup>\u0000 <mrow>\u0000 <mi>H</mi>\u0000 <mi>e</mi>\u0000 </mrow>\u0000 <mo>+</mo>\u0000 </msup>\u0000 </mrow>\u0000 </mrow>\u0000 <annotation> ${mathrm{H}mathrm{e}}^{+}$</annotation>\u0000 </semantics></math>, mesoscale and fine-scale <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mrow>\u0000 <msup>\u0000 <mi>O</mi>\u0000 <mo>+</mo>\u0000 </msup>\u0000 </mrow>\u0000 </mrow>\u0000 <annotation> ${mathrm{O}}^{+}$</annotation>\u0000 </semantics></math> structures grow more strongly correlated with protons, and light-ion correlation decreases. The average plume ion bulk flow is sunward and consistent with <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mrow>\u0000 <mn>14</mn>\u0000 <mi>%</mi>\u0000 </mrow>\u0000 </mrow>\u0000 <annotation> $14%$</annotation>\u0000 </semantics></math> penetration of the solar wind electric field. From Fourier analysis, FSS scale sizes extend down to the lower limit of the instrumental sampling range, with evidence of structures below that limit but too small to measure. Plume events exhibit discrete peaks in the Fourier spectrum, but the specific peak structure changes with event. As dayside plumes age, global FSS spectral power migrates radially outward, and shifts to smaller spatial scales. Power-law fitting of density spectra suggests that turbulence is involved in generating FSS, possibly aided by convective elongation of existing structure and the gradient-drift instability.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 10","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145317498","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 Long-Term Trend of Thermospheric Compositions From Whole Atmospheric Simulation and Satellite Observation","authors":"Chih-Ting Hsu,&nbsp;Wenbin Wang,&nbsp;Liying Qian,&nbsp;Ercha Aa,&nbsp;Joseph M. Mclnerney,&nbsp;Shun-Rong Zhang,&nbsp;Yongliang Zhang,&nbsp;Anastasia Newheart,&nbsp;Dong Lin","doi":"10.1029/2025JA034285","DOIUrl":"https://doi.org/10.1029/2025JA034285","url":null,"abstract":"&lt;p&gt;This study examines the long-term trend of column-integrated atomic oxygen to molecular nitrogen ratio, &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;Σ&lt;/mi&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;mo&gt;/&lt;/mo&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;N&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${Sigma }O/{N}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, in the upper atmosphere and investigates the cause of this long-term trend in &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;Σ&lt;/mi&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;mo&gt;/&lt;/mo&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;N&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${Sigma }O/{N}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;. We first validate the feasibility of using a physics-based model for a long-term climate reanalysis by applying a model-data comparison between 2002 and 2018. &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;Σ&lt;/mi&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;mo&gt;/&lt;/mo&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;N&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${Sigma }O/{N}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; simulated by NSF NCAR's Whole Atmosphere Community Climate Model (WACCM) with thermosphere and ionosphere extension (WACCM-X) and measured by Global Ultraviolet Imager (GUVI) aboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) mission is used to determine the long-term trend of &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;Σ&lt;/mi&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;mo&gt;/&lt;/mo&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;N&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${Sigma }O/{N}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; from 2002 to 2018 and validate the model result. The model and data show good agreement after removing the impact of solar irradiance and geomagnetic activity using a least-squares fitting method, revealing a decreasing trend of &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;Σ&lt;/mi&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;mo&gt;/&lt;/mo&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;N&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${Sigma }O/{N}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; of about &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;0.54&lt;/mn&gt;\u0000 &lt;mi&gt;%&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 ","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 10","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145317053","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":"Low Plasma Density Estimation Based on Measurements of Electron Cyclotron Harmonic Waves","authors":"Didier Mourenas,&nbsp;Ruoxian Zhou,&nbsp;Xiao-Jia Zhang,&nbsp;Anton V. Artemyev","doi":"10.1029/2025JA034459","DOIUrl":"https://doi.org/10.1029/2025JA034459","url":null,"abstract":"<p>The electron plasma frequency to cyclotron frequency ratio is a crucial parameter for accurately evaluating local chorus wave-driven electron acceleration and loss in the inner magnetosphere. In the present work, we propose a method for inferring the plasma frequency from near-equatorial measurements of electron cyclotron harmonic (ECH) waves in low plasma density regions outside the plasmasphere. The basic procedure first consists in a careful selection of ECH waves, such that their frequencies at peak power in two consecutive cyclotron harmonic bands are consistent with their theoretical maximum frequency in these bands. Next, the equatorial plasma frequency can be inferred based on the retained wave measurements, under the assumption of an approximately Maxwellian or Kappa electron distribution (possibly including a small fraction of significantly more energetic electrons). This method has been validated through comparisons with the plasma frequency inferred from the upper hybrid resonance during 16 events that took place during geomagnetic storms in 2014–2018, using data from the Van Allen Probes. The error made with the new method compared to the upper hybrid resonance method usually remains moderate, suggesting that this new method could be a useful complement to the previous methods. However, caution should be exerted when using this method, due to its sensibility to small uncertainties in the electron cyclotron frequency. It is also inapplicable in the presence of a hot electron population of similar or higher density than the cold/cool population.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 10","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA034459","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145316921","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":"Fast Computerized Ionospheric Tomography Using GNSS-TEC in Densely Observed Regions","authors":"Satoru Yoneyama,&nbsp;Ken Umeno","doi":"10.1029/2024JA033404","DOIUrl":"https://doi.org/10.1029/2024JA033404","url":null,"abstract":"<p>In recent years, the range of technologies affected by the ionosphere has been steadily expanding. Technologies such as Global Positioning System, which have become indispensable in modern society, can suffer from degraded accuracy due to ionospheric structures. To meet these needs, it is essential to estimate ionospheric structures with both low latency and high resolution. However, research addressing this issue has been limited. In this study, we propose an algorithm for effective ionospheric tomography over large regions where high-density observation data are available. The algorithm exploits the fact that ionospheric electron density remains relatively stable over the 30-s sampling interval of Total Electron Content (TEC) measurements, using the most recent known distribution as an initial guess for the unknown distribution and a conjugate gradient method with diagonal scaling preprocessing to significantly accelerate the convergence of the solution. When applied to actual data, the proposed algorithm successfully estimated electron density distributions over the entire region of Japan with a spatial resolution of 0.25° mesh, using TEC data sampled at 1-min intervals. This result demonstrates the effectiveness of the proposed method. Additionally, the algorithm was used to evaluate seasonal variations in the structure of Medium-Scale Traveling Ionospheric Disturbances. The findings indicate that high-resolution and high-accuracy tomography enables detailed analysis of ionospheric structures.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 10","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA033404","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145316981","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":"Multiple-Event Study of Substorm Electric Field Penetration Into Middle Latitudes Based on Simultaneous Observation of 630-nm Airglow Enhancements at Three Stations","authors":"S. Morita,&nbsp;K. Shiokawa,&nbsp;Y. Otsuka,&nbsp;N. Nshitani,&nbsp;A. Shinbori,&nbsp;A. Fujimoto,&nbsp;A. Yoshikawa,&nbsp;M. Nishioka,&nbsp;S. Perwitasari,&nbsp;M. Yamamoto,&nbsp;T. Sori","doi":"10.1029/2025JA033721","DOIUrl":"https://doi.org/10.1029/2025JA033721","url":null,"abstract":"<p>It is known that convection electric fields develop in the polar region associated with substorm onset, and a westward electric field penetrates to lower latitudes on the night side. Two-dimensional observations of 630-nm airglow enhancements associated with the westward electric field can be conducted using all-sky cameras at middle latitudes. We investigated seven simultaneous 630-nm airglow enhancement events using all-sky cameras at Rikubetsu (43.5°N, 143.8°E), Shigaraki (34.9°N, 136.1°E), and Sata (31.0°N, 130.7°E) in Japan. A multi-event multi-point study of 630-nm airglow enhancement has been conducted for the first time. These seven events were found from 1,800 nights in 11 years, from 2002 to 2012, indicating that simultaneous 630-nm airglow enhancements over Japan were very rare. Five of these events occurred during storms, suggesting that simultaneous enhancement requires a large penetrating electric field associated with storm-time substorms. In three events, the enhancement was identified as occurring simultaneously with clear substorm onsets, while the other four events were also associated with high-latitude magnetic disturbances. In all seven events, we observed downward motion of the ionosphere associated with the airglow enhancement. These results indicate that they are due to the westward electric field in the substorm undershielding state. In two events, the time at the end of the 630-nm airglow enhancement correlated well with the increase in ionospheric altitude observed by ionosondes and an FM-CW radar. This increase in ionospheric altitude and termination of the airglow enhancement could be caused by eastward electric field penetration associated with overshielding in the magnetosphere.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 10","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA033721","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145316910","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":"Local Time Dependence of High-Latitude Pc5 Wave Activity Driven by Interplanetary Shocks and Foreshock Transients, Using a New ULF Index","authors":"Veera Lipsanen,&nbsp;Lucile Turc,&nbsp;Sanni Hoilijoki,&nbsp;Denny M. Oliveira,&nbsp;Souhail Dahani,&nbsp;Shi Tao,&nbsp;Milla Kalliokoski,&nbsp;Mirja Ojuva,&nbsp;Emilia K. J. Kilpua","doi":"10.1029/2025JA034378","DOIUrl":"https://doi.org/10.1029/2025JA034378","url":null,"abstract":"<p>We present a study of ground-based Pc5 ultra-low frequency (ULF) wave response to over 400 interplanetary (IP) shocks and 18 foreshock transients. We investigated the local time dependence of magnetospheric Pc5 wave power generated by IP shocks and foreshock transients and whether this dependence is related to the impact angle of IP shocks and impact point of foreshock transients. To study this, we created a new magnetic local time dependent high-latitude Pc5 ULF wave index using magnetic field measurements from high latitude magnetometers obtained from SuperMAG. Our findings indicate that the impact angle of an IP shock does not determine the location of the peak Pc5 power. However, we find that frontal shocks drive stronger wave power than inclined shocks. Shock speed and dynamic pressure ratio correlate moderately with the peak Pc5 power. During 61% of the studied foreshock transients, we observe a clear Pc5 response, that is, the wave power increased significantly. The distribution of Pc5 power is consistent with the propagation direction of the transients. The results suggest that the size of the foreshock transient and the solar wind speed may affect the observed Pc5 wave response. Although the Pc5 response to IP shocks and foreshock transients differ, foreshock transients can drive Pc5 wave power comparable to IP shocks.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 10","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA034378","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145272358","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":"IMF Control of Electron Aurora Across Mars' Crustal Magnetic Fields: Insights Into Electron Sources","authors":"Robert J. Lillis,&nbsp;Yingjuan Ma,&nbsp;Shaosui Xu,&nbsp;Justin Deighan,&nbsp;Krishnaprasad Chirakkil,&nbsp;Sonal Jain,&nbsp;Matthew Fillingim,&nbsp;Michael Chaffin,&nbsp;Greg Holsclaw,&nbsp;Scott England,&nbsp;Raghuram Susarla,&nbsp;David Brain,&nbsp;Hoor Al Mazmi,&nbsp;Abigail R. Azari,&nbsp;Yaxue Dong,&nbsp;Nick Schneider,&nbsp;Jared Espley,&nbsp;Shannon Curry","doi":"10.1029/2025JA033913","DOIUrl":"https://doi.org/10.1029/2025JA033913","url":null,"abstract":"<p>We investigate Martian electron aurora utilizing 130.4 nm auroral observations from the Emirates Mars Ultraviolet Spectrograph and IMF clock angle measurements and estimates from MAVEN. Analysis reveals that more than 5 R aurora occurrence in a given region can vary by up to a factor of seven with IMF orientation, generally highest for southward IMF and lowest for westward IMF, with higher auroral occurrence post-dusk, decreasing toward and past midnight before increasing again toward dawn. A broad diversity of IMF and local time dependence of aurora occurrence is observed across Mars' crustal magnetic fields. The polarity of a given crustal field determines whether its field lines preferentially magnetically connect to dayside ionospheric or nightside magnetotail electron sources in the post-dusk or pre-dawn sectors. We thus establish a “source preference metric”, that is, the excess likelihood of aurora when likely magnetically connected to the nightside versus dayside. A wide range of source preferences are observed across the crustal field features, with some showing higher occurrence for night sources, day sources, or neither, often differently when in the post-dusk or pre-dawn sectors. A generally stronger nightside source preference is found for radially inward crustal fields in the predawn sector, and for weaker outward crustal fields in the post-dusk sector. These results highlight the complex and dynamic nature of Mars' magnetic topology in controlling auroral electron access. Future studies integrating in situ electron measurements with synoptic and limb auroral imaging will further constrain the relative contributions of dayside and magnetotail electron populations to Mars' auroral processes.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 10","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145272434","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}