Journal of Geophysical Research: Space Physics最新文献

{"title":"Ion Phase Space Density Profiles Within the Magnetosphere of Saturn: Investigating the Source of Suprathermal Ions","authors":"R. C. Allen,&nbsp;S. K. Vines,&nbsp;C. P. Paranicas,&nbsp;W. Mo,&nbsp;K. Dialynas","doi":"10.1029/2024JA033563","DOIUrl":"https://doi.org/10.1029/2024JA033563","url":null,"abstract":"<p>Phase space density (PSD) profiles at fixed values of the first two adiabatic invariants (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>μ</mi>\u0000 </mrow>\u0000 <annotation> ${upmu }$</annotation>\u0000 </semantics></math>; magnetic moment and <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>k</mi>\u0000 </mrow>\u0000 <annotation> $k$</annotation>\u0000 </semantics></math>; longitudinal invariant) versus <i>L</i> shell provide a quantitative way to investigate the sources, losses, and radial transport of plasma and energetic charged particles within a planetary magnetosphere. PSD profiles have been obtained from the Magnetosphere Imaging Investigation/Charge-Energy-Mass Spectrometer (MIMI/CHEMS) for H⁺, W⁺, O⁺⁺, H₂⁺, He⁺, and He⁺⁺ for the period Cassini was in orbit around Saturn (July 2004 until September 2017). Beyond the expected variations for all species due to the suprathermal spectral slopes, the PSD profiles also show significantly more loss for lower <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>k</mi>\u0000 </mrow>\u0000 <annotation> $k$</annotation>\u0000 </semantics></math> (i.e., more equatorially mirroring or “trapped”) populations. This dependency of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>k</mi>\u0000 </mrow>\u0000 <annotation> $k$</annotation>\u0000 </semantics></math> for loss is consistent with higher loss rates of trapped populations in the inner magnetosphere (&lt;10 R_S) due to neutral densities being more equatorially confined. The PSD radial profiles of all species, regardless of solar wind-origin (e.g., H⁺, He⁺, He⁺⁺) or magnetospheric-origin (e.g., H⁺, W⁺, H₂⁺, and O⁺⁺), indicate that the outer magnetosphere is the predominant region of non-adiabatically accelerated lower energy plasma that may be a source of the suprathermal ions. Mission-averaged PSD profiles are also used along with the computed PSD profile near an interchange injection event to estimate the original <i>L</i> shell of injected H⁺ and W⁺ ions. For this injection event, the estimated source of both the H⁺ and W⁺ ions was between 1 and 2 Saturn radii (R_S) away, consistent with previous studies of interchange injection events at Saturn.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 3","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA033563","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143513843","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":"Low-Latitude Ionospheric Responses to the Severe Geomagnetic Storm During 23–25 April 2023 Over the American Sector","authors":"Pengfei Hu,&nbsp;Gang Chen,&nbsp;Shaodong Zhang,&nbsp;Wanlin Gong,&nbsp;Min Zhang","doi":"10.1029/2024JA033692","DOIUrl":"https://doi.org/10.1029/2024JA033692","url":null,"abstract":"<p>The impacts of the severe geomagnetic storm on 23–25 April 2023 on the low-latitude ionosphere over the American sector are investigated. Based on the ground-based and spaceborne instruments, a series of storm-associated ionospheric disturbances have been observed as follows: (a) The eastward Prompt Penetration Electric Fields intensified the equatorial upward <i>E</i> × <i>B</i> drift, and enhanced the Equatorial Ionization Anomaly (EIA) during the first main phase. (b) The EIA asymmetry in the region east of 70°W and one-sided F3 layer in the northern hemisphere are observed and are attributed to the strong southward transequatorial winds. (c) The disturbances of electric field and neutral winds raised the low-latitude and equatorial F-layer dramatically, and generated post-midnight Equatorial Plasma Bubbles. These bubbles rapidly extended to the magnetic latitude of 30°, corresponding to a rare Apex altitude of ∼2,600 km at magnetic equator. (d) On 24 April, the thermospheric composition disturbances with high ΣO/N₂ were concentrated in the southern hemisphere, and resulted in the positive storm over South America.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 3","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143513487","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":"Asymmetry in the Ring Current During Geomagnetic Disturbances","authors":"G. E. Bower,&nbsp;S. E. Milan,&nbsp;S. Imber,&nbsp;A. Schillings,&nbsp;A. Fleetham,&nbsp;C. Beggan,&nbsp;J. W. Gjerloev","doi":"10.1029/2024JA033492","DOIUrl":"https://doi.org/10.1029/2024JA033492","url":null,"abstract":"<p>Geomagnetic disturbances (GMDs) are defined as rapid changes in the magnetic field of the Earth that can lead to geomagnetically induced currents (GICs). Recent studies have shown that there are two main populations of GMDs, one in the pre-midnight sector and one in the dawn sector. The pre-midnight GMDs have been related to the substorm current wedge. The dawn population of GMDs has previously been found to occur during multiple intensification events. We adapt the SOPHIE substorm list to identify more instances of multiple intensifications. Recent models suggest the formation of a “dawnside current wedge” (DCW) during the main phase of storms that could lead to dawn sector GMDs. We investigate GMDs at all latitudes using the SuperMAG local time indices (SMR-LT), where SMR-LT are local time measurements of the magnetic field at low latitudes. During multiple intensification events the dawn sector low latitude magnetic field between 3 and 9 MLT (SMR06) is typically higher than the dusk sector between 15 and 21 MLT (SMR18), which is indicative of a DCW. Statistical analysis of the local time ring current indices during the dawn and pre-midnight GMDs shows that the dawn GMDs occur when the difference between the dawn sector and dusk sector SMR values (SMR06-SMR18) is largest and thus when there is a DCW.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 3","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA033492","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143489838","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":"Identifying the Growth Phase of Magnetic Reconnection Using Pressure-Strain Interaction","authors":"M. Hasan Barbhuiya,&nbsp;Paul A. Cassak,&nbsp;Alex Chasapis,&nbsp;Michael A. Shay,&nbsp;Giulia Cozzani,&nbsp;Alessandro Retinò","doi":"10.1029/2024JA033446","DOIUrl":"https://doi.org/10.1029/2024JA033446","url":null,"abstract":"<p>Magnetic reconnection often initiates abruptly and then rapidly progresses to a nonlinear quasi-steady state. While satellites frequently detect reconnection events, ascertaining whether the system has achieved steady-state or is still evolving in time remains challenging. Here, we propose that the relatively rapid opening of the reconnection separatrices within the electron diffusion region serves as an indicator of the growth phase of reconnection. The opening of the separatrices is produced by electron flows diverging away from the neutral line downstream of the X-line and flowing around a dipolarization front. This flow pattern leads to characteristic spatial structures in the electron pressure-strain interaction that could be a useful indicator for the growth phase of a reconnection event. We employ two-dimensional particle-in-cell numerical simulations of anti-parallel magnetic reconnection to validate this prediction. We find that the signature discussed here, alongside traditional reconnection indicators, can serve as a marker of the growth phase. This signature is potentially accessible using multi-spacecraft single-point measurements, such as with NASA's Magnetospheric Multiscale satellites in Earth's magnetotail. Applications to other settings where reconnection occurs are also discussed.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 3","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143497276","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Statistical Analysis of Van Allen Probes-B Observations of Stable Auroral Red Arc Intervals in the Overlap Region Between the Plasmasphere and the Ring Current","authors":"Rei Sugimura,&nbsp;Kazuo Shiokawa,&nbsp;Yoshizumi Miyoshi,&nbsp;Charles Smith,&nbsp;Harlan Spence,&nbsp;Geoff Reeves","doi":"10.1029/2024JA032893","DOIUrl":"https://doi.org/10.1029/2024JA032893","url":null,"abstract":"<p>In Earth's inner magnetosphere low-energy-density plasma in the plasmasphere (PS) partially overlaps with higher-energy plasma in the ring current (RC). Auroral emissions with zonally elongated arc-like shapes called Stable Auroral Red (SAR) arcs occur in the subauroral latitudes that are connected to the inner magnetosphere. There has yet to be a statistical analysis of the PS-RC overlap region in which SAR arcs occur. We conducted a statistical analysis of the occurrence characteristics of this PS-RC overlap region for SAR arcs, using the RBSP-B satellite over a 4-year period from 1 January 2015 to 31 December 2018. We defined the PS-RC overlap region based on ground-satellite conjugate observations of SAR arcs on the same geomagnetic field line. The overlap region in which SAR arcs develop is located at pre-midnight for high-energy oxygen ions and post-midnight for low-energy hydrogen ions. Superposed epoch analysis using the SYM-H index shows that the PS-RC overlap occurs near the end of the main phase of magnetic storms for both H⁺ and O⁺ ions, indicating that the SAR arc source develops at the particle injection during the end of the storm's main phase. Superposed epoch analysis using the SML index revealed that several substorms occurred near the onset time of the SAR arc source for both ion species. This suggests that particle injection by substorms at the end of the magnetic storm is important for the formation of the SAR arc source.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 3","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA032893","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143497275","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":"Large-Scale Field-Aligned Currents Around the High-Latitude Energetic Electron Boundary: FY-3E Observations","authors":"Jie Ren,&nbsp;Qiu-Gang Zong,&nbsp;Yongfu Wang,&nbsp;Xiangqian Yu,&nbsp;Zi-Jian Feng,&nbsp;Ting-Yan Xiang,&nbsp;Xin-Yu Ai","doi":"10.1029/2025JA033710","DOIUrl":"https://doi.org/10.1029/2025JA033710","url":null,"abstract":"<p>The recently launched Fengyun-3E (FY-3E) satellite in the early morning orbit can simultaneously measure magnetic fields and energetic electrons, which provides a good opportunity to investigate the distribution and variation of large-scale field-aligned currents (FACs) in the dawnside and duskside of both hemispheres. Based on the statistical results with one and a half years of data, we find that the location of region 1 (R1) and region 2 (R2) currents is closely associated with the high-latitude energetic electron boundary, these FACs in the northern hemisphere are preferentially located in higher magnetic latitudes than in the southern hemisphere especially during geomagnetic quiet time, and the location of FACs has a larger equatorward motion than the electron boundary during active time. The location and current intensity of FACs in different sectors of Earth's magnetosphere are quantified as a function of the Kp index, the Sym-H index and the interplanetary magnetic field (IMF) <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>. Comparisons between different sectors also indicate that the current intensities of both R1 and R2 currents have a north-south asymmetry, and they are stronger in the dawnside northern hemisphere than other sectors. These findings may shed new light on our understanding of the spatial distribution and evolution of large-scale FACs in Earth's magnetosphere.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 3","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143497274","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 Spreading of Magnetic Reconnection X-Line in Particle-In-Cell Simulations– Mechanism and the Effect of Drift-Kink Instability","authors":"Shan-Chang Lin,&nbsp;Yi-Hsin Liu,&nbsp;Xiaocan Li","doi":"10.1029/2024JA033494","DOIUrl":"https://doi.org/10.1029/2024JA033494","url":null,"abstract":"<p>Using three-dimensional particle-in-cell (PIC) simulations, we study the spread of magnetic reconnection X-line. We show that structural asymmetries along the X-line direction develop during its spread. On the plane of the current sheet (i.e., corresponding to the equatorial plane of the magnetotail), sharp cusp-shaped signatures develop along the ion-drifting direction, capturing the spread of the X-line. The spreading is catalyzed by the lower ion pressure from the active diffusion region, and the X-line spreads at the ion-drifting speed of the non-reconnecting current sheet. Along the electron-drifting direction, the X-line barely spreads even though the electron-drifting speed is high within the electron diffusion region, and reconnected flux is transported toward this direction by the Hall effect. This preferential spread in the ion-drifting direction provides an additional explanation for the higher occurrence rate of reconnection events on the dusk side in Earth's magnetotail. In contrast to the laminar X-line, in a companion run, we demonstrate that the fluctuation and turbulence caused by drift-kink instability only suppress the X-line spreading. Even though the fluctuation breaks the frozen-in condition, it does not lead to the continuous onset of reconnection adjacent to the active region.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 2","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143471984","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":"Characteristics of Wave-Particle Power Transfer as a Function of Electron Pitch Angle in Nonlinear Frequency Chirping","authors":"Zeyin Wu,&nbsp;Yifan Wu,&nbsp;Xin Tao","doi":"10.1029/2024JA033458","DOIUrl":"https://doi.org/10.1029/2024JA033458","url":null,"abstract":"<p>Whistler mode chorus waves, common in Earth's and planetary magnetospheres, play a crucial role in energetic electron dynamics. These waves exhibit distinctive narrowband features, intense amplitudes, and frequency chirping. While numerous studies have explored chorus wave generation, an important yet often overlooked parameter is the resonant electron pitch angle. Motivated by this gap, we conduct particle-in-cell (PIC) simulations to identify the key pitch angle governing wave-particle power transfer during interactions with chorus waves. Our findings reveal that the characteristic pitch angle, which dominates power transfer, aligns with the pitch angle that minimizes the nonlinear parameter during the central portion of a chirping element. This insight supports the use of a representative pitch angle in nonlinear theories of chorus waves to estimate wave properties.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 2","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143456029","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":"A 3-D FDTD Methodology for Modeling the Propagation of VLF Whistler Mode PLHR Waves Through the Ionosphere","authors":"A. S. Pedgaonkar,&nbsp;J. J. Simpson,&nbsp;E. A. Jensen","doi":"10.1029/2024JA033273","DOIUrl":"https://doi.org/10.1029/2024JA033273","url":null,"abstract":"<p>The finite-difference time-domain (FDTD) method was previously applied to high-frequency electromagnetic wave propagation through 250 km of the <i>F</i> region of the ionosphere. That modeling approach was limited to electromagnetic wave propagation above the critical frequency of the ionospheric plasma, and it did not include the lower ionosphere layers or the top of the <i>F</i>-region. This paper extends the previous modeling methodology to frequencies below the critical frequency of the plasma and to altitudes encompassing the ionosphere. The following changes to the previous work were required to generate this model: (a) the <i>D</i>, <i>E</i> and top of the <i>F</i> regions of the ionosphere were added; and (b) the perfectly matched layer absorbing boundary on the top side of the grid was replaced with a collisional plasma to prevent reflections. We apply this model to the study of extremely low frequency (ELF) and very low frequency (VLF) electric power line harmonic radiation (PLHR) through the ionosphere. The model is compared against analytical predictions and applied to PLHR propagation in polar, mid-latitude and equatorial regions. Also, to further demonstrate the advantages of the grid-based FDTD method, PLHR propagation through a polar cap patch with inhomogeneities is studied. The presented modeling methodology may be applied to additional scenarios in a straightforward manner and can serve as a useful tool for better tracking and studying electromagnetic wave propagation through the ionosphere at any latitude and in the presence of irregularities of any size and shape.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 2","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA033273","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143456025","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":"“Polar” Substorms During Slow Solar Wind","authors":"I. V. Despirak,&nbsp;N. G. Kleimenova,&nbsp;A. A. Lubchich,&nbsp;P. V. Setsko,&nbsp;L. M. Malysheva","doi":"10.1029/2024JA033555","DOIUrl":"https://doi.org/10.1029/2024JA033555","url":null,"abstract":"<p>“Polar” substorms are identified as substorm-like disturbances that are exclusively observed at high geomagnetic latitudes (&gt;70° MLAT) and are absent at lower latitudes. Although “polar” substorms typically occur during periods of quiet geomagnetic activity, it is still unclear whether they can develop under extremely quiet conditions when geoeffective space weather parameters are exceptionally low. Utilizing data from the IMAGE network across the Svalbard archipelago within the longitudinal sector of (∼108–114 Mlong), we examined 92 “extremely quiet geomagnetic” intervals from 2010 to 2020, which were associated with intervals of extremely slow solar wind (ESSWs, <i>V</i> &lt; 300 km/s). We discovered that “polar” substorms can occur during ESSWs, but only with the presence of a negative Bz component. A total of 32 such events were identified from 17 ESSW intervals (∼19% of all ESSW intervals). We found that “polar” substorms during ESSWs display the primary characteristics of ordinary substorms, including the accompaniment of Pi1B geomagnetic pulsations, positive subauroral or mid-latitude magnetic bays, a poleward shift of the westward electrojet, and auroral activity during their expansion phase. Additionally, it was found that the majority of “polar” substorm events during ESSWs (∼82%) were isolated substorms, developing solely in the pre-midnight sector without disturbances in other longitudinal sectors. Several “polar” substorm events have been examined in detail.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 2","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143456028","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}