Journal of Geophysical Research: Space Physics最新文献

{"title":"Effects of Solar Flares on the Ionosphere of Mars: Comparison of Observed and Predicted Electron Density Profiles From 15 to 26 April 2001","authors":"Paul Withers,&nbsp;A. G. Cramer,&nbsp;D. J. Pawlowski","doi":"10.1029/2024JA033197","DOIUrl":"https://doi.org/10.1029/2024JA033197","url":null,"abstract":"<p>Solar flares significantly affect Mars's ionosphere, yet there are few comparisons between observed and simulated densities in the M1 and M2 ionospheric layers during solar flares. Here we compare observed and simulated electron density profiles for the X14.4 solar flare of 15 April 2001 and the M7.8 solar flare of 26 April 2001. We use observations from Mars Global Surveyor radio occultations and simulations from the Mars Global Ionosphere-Thermosphere Model (M-GITM). Due to poor constraints on the solar spectrum incident upon Mars at this time, simulated M2 electron density values were 50% larger than observed. Yet the relative changes in M2 electron density during these two flares were reproduced to 10% accuracy. When accurate solar irradiance data are available, absolute M2 electron density values are simulated accurately. Due to the omission of electron impact ionization from the M-GITM model, the simulated M1/M2 density ratio was under-predicted by a factor of approximately 3. Yet the relative changes in M1 electron density during these two flares were reproduced to 20% accuracy. The model can accurately predict relative changes in M1 and M2 electron densities during a solar flare. If accurate solar irradiance data are available, it can accurately predict absolute changes in M2 electron densities. If a simple parameterization of electron impact ionization were incorporated into the model, then it would likely predict absolute changes in M1 electron densities accurately as well. The M-GITM model is well-suited to studies of time-varying phenomena in the ionosphere of Mars.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144220346","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 Radio Wave Polarization of Saturn Lightning Observed by Cassini","authors":"G. Fischer,&nbsp;M. Imai,&nbsp;U. Taubenschuss,&nbsp;D. Píša,&nbsp;W. S. Kurth","doi":"10.1029/2024JA033560","DOIUrl":"https://doi.org/10.1029/2024JA033560","url":null,"abstract":"<p>We investigate the polarization of the radio waves emitted by lightning in Saturn's atmosphere, which are referred to as SEDs for Saturn Electrostatic Discharges. Using the complete SED data set retrieved by Cassini's RPWS (Radio and Plasma Wave Science) instrument we found that the circular polarization of SEDs below a frequency of 2 MHz depends on the latitudinal hemisphere of the lightning storm. SEDs from several storms located at <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>35</mn>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <annotation> $35{}^{circ}$</annotation>\u0000 </semantics></math> South latitude display a strong right–hand sense of circular polarization, whereas SEDs from storms located at <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>35</mn>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <annotation> $35{}^{circ}$</annotation>\u0000 </semantics></math> and <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>50</mn>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <annotation> $50{}^{circ}$</annotation>\u0000 </semantics></math> North are overwhelmingly left–hand polarized. A single storm located at Saturn's equator in June 2005 shows 4 right–handed SEDs when Cassini was in the northern hemisphere and 4 left–handed SEDs when Cassini was in the southern hemisphere. The polarization characteristic is consistent with an emission in the L-O mode, consistent with the theory of Fischer, Gurnett, et al. (2007, JGR 112, A12308, https://doi.org/10.1029/2007JA012592) that the R-X mode is largely absorbed in Saturn's ionosphere below a frequency of 2 MHz. The sense of circular SED polarization below 2 MHz is opposite to the polarization of Saturn kilometric radiation (SKR), and thus this can be used to distinguish SEDs from SKR and to determine the hemispherical origin of the causative lightning storm.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA033560","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144220345","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":"Substorm Event Retrieval Model in Ultraviolet Aurora Images Based on Contextual CNN Features","authors":"Ze-Jun Hu,&nbsp;Bing Han,&nbsp;Bairu Zhao,&nbsp;Yang Lu,&nbsp;Yi-Sheng Zhang,&nbsp;Bei-Chen Zhang","doi":"10.1029/2025JA033983","DOIUrl":"https://doi.org/10.1029/2025JA033983","url":null,"abstract":"<p>Auroral substorms are one of the disturbance phenomena caused by high-energy charged particles from the solar wind precipitating into the Earth's magnetosphere and colliding with charged particles within the magnetosphere. Understanding the occurrence and evolution of substorms can help elucidate the physical processes governing the interaction between the solar wind and Earth's magnetosphere. Currently, ground-based and satellite-based imaging equipment have captured a vast amount of aurora images, and identifying auroral substorm events from these images is crucial for studying solar-terrestrial relations. The westward traveling surge (WTS) is a typical structure during substorm occurrences and is commonly used for auroral substorm identification. In this paper, we propose a method based on convolutional neural networks (CNNs) that uses a polar region partitioning strategy to locate image keypoints and determine the position and size of regional blocks. Multi-scale contextual CNN features are then generated to retrieve substorm events from ultraviolet aurora images. The results show that the multi-scale features extracted from convolutional and fully connected layers can effectively capture the characteristics of the WTS structure. The method achieves a mean average precision of 75.77% and a Recall@10 of 95.19%, demonstrating its effectiveness in retrieving auroral substorm events.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144213753","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":"Species-Dependent and Azimuthally-Directional Flux Changes of Dispersionless Ion Injections Inside Geosynchronous Orbit","authors":"T. Motoba,&nbsp;S. Ohtani","doi":"10.1029/2025JA033757","DOIUrl":"https://doi.org/10.1029/2025JA033757","url":null,"abstract":"<p>Dispersionless injection, involving sudden, simultaneous flux enhancements of energetic particles over a broad range of energy, is a characteristic signature of the particles that are experiencing a significant acceleration and/or rapid inward transport process. To provide clues to the physical processes that lead to the acceleration and transport of energetic ions in the dispersionless injection region, we conduct superposed epoch analyses of 75 dispersionless injection events identified by Van Allen Probes with focus on the species- and azimuthal angle- (<i>φ</i>) dependent signatures of ∼50–600 keV ions inside geosynchronous orbit. Our analysis shows that, on average, the light (hydrogen and helium) ion fluxes undergo a rapid, transient enhancement, while the heavy (oxygen) ion fluxes exhibit a more gradual, persisting enhancement. Such a species-dependent behavior could be explained in terms of different gyro-radius of the ion species. For events where the proton injection onset is 30–60 s earlier than the electron one, proton fluxes initially increase at small <i>φ</i> values (i.e., tailward guiding centers) and then at larger <i>φ</i> values (earthward ones). The initial signatures suggest a result of the earthward transport of injected protons, as seen at the explosive growth phase. For events where both electron and proton fluxes increase simultaneously, on the other hand, proton fluxes isotropically increase with no significant <i>φ</i> dependence. Such an isotropic proton flux enhancement may imply a local process in which charged protons are rapidly accelerated to higher energies at the spacecraft location.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA033757","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144214189","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":"Periodic Density Structures Around the Plasmaspheric Plume Boundary and Their Association With ULF Waves","authors":"Ting-Yan Xiang,&nbsp;Jie Ren,&nbsp;Qiu-Gang Zong,&nbsp;Zi-Jian Feng,&nbsp;Xin-Yu Ai","doi":"10.1029/2025JA034044","DOIUrl":"https://doi.org/10.1029/2025JA034044","url":null,"abstract":"<p>Here we report that the dynamics of the plasmaspheric plume can be affected by ULF waves based on observations from Van Allen Probes. Probe A observed periodic density structures with regular waveforms when traveling into the plume from its western boundary on 19 August 2013. The crests of the density structures were filled with intense hiss waves and low-energy <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msup>\u0000 <mi>H</mi>\u0000 <mo>+</mo>\u0000 </msup>\u0000 </mrow>\u0000 <annotation> ${mathrm{H}}^{+}$</annotation>\u0000 </semantics></math> that also appeared in the plume. The in-phase relationship between toroidal magnetic field perturbations and density structures in the northern hemisphere indicates that the plume boundary was stretched westward when the field lines were moving westward. These observations indicate that periodic density structures stem from the azimuthal oscillations of the plume boundary under the drive of the fundamental toroidal mode of ULF waves. ULF waves around the plume boundary exhibit the largest amplitude and out-of-phase polarization, and the polarization is changing with MLT across the plume boundary, demonstrating that field line resonance (FLR) occurred at the plume boundary. These observations are consistent with the theoretically predicted characteristics of 3-D FLR associated with the plamspheric plume.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144213788","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":"Mesopause Insights: Unraveling Temperature and Height Trends Through SABER/TIMED and SD WACCM X Simulations","authors":"M. Pramitha,&nbsp;M. Praveen,&nbsp;M. Venkat Ratnam","doi":"10.1029/2024JA033457","DOIUrl":"https://doi.org/10.1029/2024JA033457","url":null,"abstract":"<p>As human activities and climate change continue to affect the middle atmosphere, understanding long-term changes in atmospheric parameters has become critical. This study uses the data from the SABER/TIMED satellite to analyze global variations in mesopause temperature and height, and evaluates the performance of the Specified dynamics–Whole atmosphere community climate model extended (SD-WACCM X) in reproducing these variations. A bias correction using the cumulative distribution function Quantile mapping was applied to SD WACCM X data based on SABER observations. The correction reveals a positive bias of up to 9.2 K at specific altitudes in the Southern (94–102 km) and Northern (70–75 km) Polar regions, and up to 4.6 K in low-latitude areas (above 94 km) during January. Mesopause temperature exhibits a two-level structure, with an upper mesopause around 100 km and a lower one near 86 km, varying with latitude from 120 to 200 K. SD WACCM X generally underestimates mesopause height by 2%–17% in mid-latitude and polar summer regions. Long-term trends in mesopause height and temperature were also examined, factoring in solar cycles, and the quasi-biennial oscillations, with SABER data showing a negative temperature trend of −0.33 to −2.2 K per decade.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144214190","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":"Do Solar Eclipses Generate Propagating Ionospheric Perturbations?","authors":"Andrew K. Sun,&nbsp;Hyosub Kil,&nbsp;Hyeyeon Chang,&nbsp;Woo Kyoung Lee,&nbsp;Jiyun Lee","doi":"10.1029/2025JA033746","DOIUrl":"https://doi.org/10.1029/2025JA033746","url":null,"abstract":"<p>Plasma depletion during a solar eclipse is well-documented, but the generation of other forms of ionospheric perturbations by the impact of eclipses is controversial. This study aims to evaluate the generation of additional ionospheric perturbations through case studies of total solar eclipses observed across the United States on 21 August 2017 and 8 May 2024. Total electron content (TEC) values are used to track ionospheric perturbations along the eclipse paths. When a smoothing filter (Savitzky–Golay filter) is applied to detect ionospheric perturbations, negative TEC perturbations are observed during totality, while positive TEC perturbations are detected around the beginning and end of the eclipses. These perturbations, caused by rapid TEC variations during these periods, are interpreted as filtering artifacts. Quasi-periodic multiple TEC perturbation layers are detected along the eclipse paths when an oscillatory filter (polynomial detrending) is applied. However, as this filter introduces wave-like artifacts during detrending, the resulting patterns do not represent actual TEC perturbations. Based on our observational and test results, we conclude that eclipse-induced ionospheric perturbations beyond the well-documented plasma depletion are not evident because actual eclipse-induced perturbations are not distinguishable from filtering artifacts.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA033746","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144206935","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":"Inferential Evidence for Surprathermal Electron Burst Intensification Due To Inverted-V Precipitation via Inertial Alfvén Waves","authors":"C. Feltman,&nbsp;G. G. Howes,&nbsp;S. R. Bounds,&nbsp;D. M. Miles,&nbsp;C. A. Kletzing,&nbsp;K. Greene,&nbsp;R. Broadfoot,&nbsp;J. Bonnell,&nbsp;R. Roglans","doi":"10.1029/2025JA033869","DOIUrl":"https://doi.org/10.1029/2025JA033869","url":null,"abstract":"<p>The auroral current and electrodynamic structures II sounding rocket mission launched two payloads from Andøya Rocket Range into a post-dusk discrete auroral arc and observed field-aligned electron dispersions near inverted-V precipitation. Five repetitive suprathermal electron bursts (STEBs) associated with low frequency (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>&lt;</mo>\u0000 </mrow>\u0000 <annotation> ${&lt; } $</annotation>\u0000 </semantics></math>8 Hz) magnetic perturbations are observed on the High Flyer at 400 km altitude. Similar fluctuations on the nearby Low Flyer at 180 km are shown to be Earth-ward traveling Alfvén waves, suggesting the High Flyer also observed Alfvénic activity. The electron bursts occur both coincident and outside inverted-V electrons, with those coincident displaying the highest peak energy and average differential flux values. We interpret the events as wave-particle acceleration via inertial Alfvén waves along near-Earth field lines and employ time-of-flight methods to gauge source altitudes. A Levenberg–Marquardt fitting routine is applied to inverted-V structures near the dispersions to characterize the expected STEB source distributions. We show the differences in STEB behavior are better explained by changes in the resonant source population and not from significant variation in Alfvén wave parameters.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA033869","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144206775","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":"Variation of Model-Predicted Reconnection Voltages Applied to Uranus' Dayside Magnetosphere","authors":"S. Zomerdijk-Russell,&nbsp;J. M. Jasinski,&nbsp;A. Masters","doi":"10.1029/2025JA033834","DOIUrl":"https://doi.org/10.1029/2025JA033834","url":null,"abstract":"<p>Uranus provides a key missing piece for fundamentally understanding solar wind-magnetospheric interactions due to its location in the outer solar system. Whether the viscous-like interaction overtakes global magnetic reconnection as the dominant process at the magnetopause of the outer planets remains unresolved. Here, we present theoretical predictions of dayside reconnection voltages applied to the Uranian system under different magnetospheric configurations to assess the effectiveness of global magnetic reconnection in the driving of Uranus' magnetosphere. We find the median model-predicted dayside reconnection voltage applied to Uranus' magnetosphere is 22.4 kV. Over just one full planetary rotation, the reconnection voltages are found to vary by tens of kV under Uranus' magnetospheric configuration during its solstice and equinox seasons with fixed solar wind conditions. However, we do not find a significant difference between average voltages at the different seasons, despite the large differences in magnetospheric configuration between solstice and equinox at Uranus. An increase from ∼17 to ∼31 kV in the modeled reconnection voltages is observed when the strength of the interplanetary magnetic field is increased corresponding to expected conditions during solar maximum. Our results suggest that variability resulting from the planet's diurnal rotation and changing solar wind conditions, are more important in controlling the reconnection voltages than seasonal dependencies.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA033834","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144206915","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":"Anomalous Substorm Signatures During Sudden Solar-Wind Pressure Enhancements","authors":"Shipra Sinha,&nbsp;David G. Sibeck,&nbsp;Mei-ching Fok,&nbsp;Denny Oliveira,&nbsp;A. K. Sinha","doi":"10.1029/2025JA033758","DOIUrl":"https://doi.org/10.1029/2025JA033758","url":null,"abstract":"<p>Magnetospheric substorms, characterized by the rapid release of energy stored in the magnetotail, play a central role in space weather dynamics. These events are typically triggered by enhanced magnetic reconnection between the Earth's magnetic field and the interplanetary magnetic field (IMF). While substorms are often associated with southward IMF orientations, studies have also shown that they can occur even during northward IMF conditions, particularly when solar wind pressure pulses or strong IMF By components are present. This paper examines two unique substorm events, occurring on 06 September 2017 and 19 December 2015, where both events involved minimal IMF Bz and prolonged negative By, alongside coincident pressure pulses. Despite these similar interplanetary conditions, the ground-based magnetic field observations revealed distinct differences in the location and intensity of the auroral electrojet. On 06 September, the electrojet was strongest in the post-midnight sector, whereas on 19 December, the maximum intensity occurred in the dawn sector. Simulations using the OpenGGCM magnetohydrodynamic model reveal that the substorm onset mechanisms differed between the two events. The 06 September event followed a typical IMF By-induced pattern with a shift in onset location to post-midnight, while the 19 December event exhibited an unusual onset, with plasma splitting and propagating sunward in both pre- and post-midnight sectors. These findings suggest that pressure pulses, rather than IMF By, are responsible for large shifts in substorm onset location. The study highlights the need for further investigation into multiple reconnection sites and the role of solar wind pressure in shaping substorm evolution.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA033758","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144206494","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}