Journal of Geophysical Research: Space Physics最新文献

{"title":"Multi-Spacecraft Analysis of Dipolarization Events With Inductive, Radial Electric Fields in the Inner Magnetosphere","authors":"H. Matsui,&nbsp;R. B. Torbert,&nbsp;C. J. Farrugia,&nbsp;T. J. Metivier,&nbsp;I. J. Cohen,&nbsp;R. E. Ergun,&nbsp;J. F. Fennell,&nbsp;Yu. V. Khotyaintsev,&nbsp;P.-A. Lindqvist,&nbsp;C. T. Russell,&nbsp;R. J. Strangeway,&nbsp;D. L. Turner","doi":"10.1029/2025JA033807","DOIUrl":"https://doi.org/10.1029/2025JA033807","url":null,"abstract":"<p>Dipolarization events with inductive, radial electric fields are investigated with multi-spacecraft analysis techniques. Observations by Magnetospheric Multiscale with separations around ion scales are used to study spatial and temporal variations of these events in the inner magnetosphere. <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>J</mi>\u0000 <mo>×</mo>\u0000 <mi>B</mi>\u0000 </mrow>\u0000 <annotation> $Jtimes B$</annotation>\u0000 </semantics></math> force, magnetic pressure force, and tension force are compared based on the Taylor expansion method, which includes the curlometer technique. The magnetic pressure force, possibly related to energetic particles and magnetic flux transported from the magnetotail, tends to contribute to the <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>J</mi>\u0000 <mo>×</mo>\u0000 <mi>B</mi>\u0000 </mrow>\u0000 <annotation> $Jtimes B$</annotation>\u0000 </semantics></math> force for the background components near the equator, while the tension force, related to Alfvén waves, contributes to the fluctuating components or outside the equator. The scale length is thousands of km for the background components, probably related to meso-scale structures, while that length is tens to a thousand km for fluctuating components. The small-scale fluctuations would be related to particle acceleration. The fluctuations are inferred to be Alfvén waves with quasi-perpendicular propagation directions and with finite temperature or kinetic effects. These fluctuations could be intermittent and not self-similar between different inter-spacecraft distances. Some energy transfer from fluctuations to particles would occur.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144315249","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":"Ionospheric Responses to Two Consecutive Geomagnetic Storms of the Ascending Phase of the Solar Cycle 25 Over the Indian Sector","authors":"S. N. Remya,&nbsp;K. Unnikrishnan,&nbsp;Smitha V. Thampi,&nbsp;H. Sreekumar","doi":"10.1029/2024JA033159","DOIUrl":"https://doi.org/10.1029/2024JA033159","url":null,"abstract":"<p>This study explores how consecutive minor geomagnetic storms impacted ionospheric conditions across the Indian sector. Utilizing in situ Total Electron Content (TEC) data from SWARM(A) and ground-based Global Navigation Satellite System (GNSS) TEC, the analysis spans the Indian longitude sector during two consecutive minor storms occurring on 3–4 November 2022 and 7–8 November 2022. On 7th November 2022, a significant M5-class solar flare from Sunspot AR3141 contributed to elevated geomagnetic activity in the Indian sector. The first storm was marked by a modest daytime TEC enhancement paired with nighttime suppression, whereas the second storm elicited a consistently positive ionospheric response throughout both day and night, indicating a sustained TEC increase over the region. Observations from TIMED/GUVI confirm compositional changes during the storms, while temporal variations in the real-time model of Equatorial Electric Field (EEF) are analyzed to understand the equatorial eastward electric field dynamics over the Indian sector. GNSS-based TEC data from Changanacherry (9.45°N, 76.54°E) reveal westward Prompt Penetration Electric Fields (PPEFs) as drivers of fluctuations during the second storm. The analysis of consecutive minor storms, focusing on local time variations, offers deeper insights into their dynamics and impact while highlighting the complex interplay between solar activity, storm-time electric fields, and ionospheric responses.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144315124","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":"First Simultaneous Multi-Point Observation of the Local-Time Asymmetry of keV Ions in the Dayside Magnetosphere During the Main Phase of the Geomagnetic Storm","authors":"Megha Pandya,&nbsp;Yusuke Ebihara,&nbsp;Denny M. Oliveira,&nbsp;Marilia Samara,&nbsp;Mei-Ching Fok,&nbsp;Ankush Bhaskar,&nbsp;Cristian P. Ferradas,&nbsp;Takashi Tanaka,&nbsp;Robert Michell,&nbsp;Geoffrey Reeves,&nbsp;Jerry W. Manweiler","doi":"10.1029/2025JA033793","DOIUrl":"https://doi.org/10.1029/2025JA033793","url":null,"abstract":"<p>Our study presents the first simultaneous multi-point observation of the local-time asymmetry of 10's–100's of keV energy ion fluxes during the main phase of the geomagnetic storm that occurred on 7 September 2017. During this event, Van Allen Probe-A and Van Allen Probe-B observed two different tendencies. The ion fluxes increased by an order of magnitude in the noon-dusk sector, while decreasing by one order or more in the dawn-noon sector, offering a unique opportunity to investigate this asymmetry. Numerical simulations employing the Comprehensive Inner Magnetosphere-Ionosphere model with time-dependent electric fields from Global Magnetohydrodynamic (MHD) simulations revealed that the local time asymmetry in ion fluxes is associated with a sharp southward turning of the interplanetary magnetic field (IMF) and long-duration persistent westward electric field. These factors cause ions to drift toward the dusk sector, while preexisting ions on the dayside drift sunward and escape the inner magnetosphere. Our findings provide the first direct observational evidence of ring current asymmetry, complementing and supporting prior statistical studies and simulation results.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144300469","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":"About Forward-Facing Slow Mode Waves at the Magnetopause","authors":"Bengt U. Ö. Sonnerup,&nbsp;Richard E. Denton","doi":"10.1029/2025JA034031","DOIUrl":"https://doi.org/10.1029/2025JA034031","url":null,"abstract":"<p>We review a theoretically predicted, hyperbolic MHD feature, exhibited in the field and plasma flow at the magnetopause, namely that of upstream-traveling, slow-mode waves, first predicted in the 1950s, but, so far, not identified in spacecraft data. Today's high-quality observations at Earth's magnetopause now invites a serious attempt to check the prediction. The required theoretical background and analysis methodology is summarized and further developed. The study is limited to elongated disturbance structures, such as bulges, on the magnetopause that are approximately two-dimensional and, in their proper frame, time independent. Most of the analysis tools are applicable to data from a single spacecraft. Subsequent papers could employ data from multi-spacecraft missions, such as the four-spacecraft Magnetospheric Multi-Scale mission. Such data will permit the study of many additional details. Because they are mathematically intertwined, both elliptic and hyperbolic signatures will be examined. The three key points illustrate the important role played by magnetic-variance analysis in the study of field perturbations in the vicinity of the magnetopause. Its most common use to date has been for the analysis of the magnetic fields from spacecraft crossings of the magnetopause, where the minimum variance direction can provide an estimate, not always of high quality, of the direction normal to the magnetopause layer. In the present paper, magnetopause traversals play only a secondary role; our primary objective is to analyze field perturbations near the magnetopause, for which we show that the ideal minimum-variance direction is tangential, rather than normal, to the unperturbed magnetopause surface.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144300468","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":"Latitudinal Distributions and Harmonic Characteristics of Pc3-5 Waves in Electric Field Measured by Arase Satellite","authors":"Li Yan,&nbsp;Wenlong Liu,&nbsp;Dianjun Zhang,&nbsp;Ziyu Wang,&nbsp;Theodore E. Sarris,&nbsp;Xinlin Li,&nbsp;Xin Tong,&nbsp;Yasumasa Kasaba,&nbsp;Yoshizumi Miyoshi,&nbsp;Tomoaki Hori,&nbsp;Iku Shinohara","doi":"10.1029/2025JA033998","DOIUrl":"https://doi.org/10.1029/2025JA033998","url":null,"abstract":"<p>Ultra-Low Frequency (ULF) waves can significantly influence the acceleration and rapid loss of radiation belt electrons. Based on about 7 years of Arase measurements, we investigate the latitudinal distribution of the wave power of poloidal and toroidal modes of the electric field in the Pc3-5 band. For Pc5 waves, the wave power of both poloidal and toroidal modes increases with latitude, consistent with the latitudinal enhancement trend observed in Cluster measurements by Yan et al. (2025, https://doi.org/10.1029/2024gl112358). For Pc3-4 wave, the latitudinal distribution of the electric field ULF waves power exhibits patterns consistent with the second and higher harmonic modes, as predicted by the theoretical model described by Cummings et al. (1969, https://doi.org/10.1029/ja074i003p00778). Furthermore, the effect of <i>Kp</i> on ULF wave power increases with latitude in the Pc3-5 band. The wave power of electric field ULF waves in the Pc3-5 band is approximately 3–4 times higher for <i>Kp</i> <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>&gt;</mo>\u0000 </mrow>\u0000 <annotation> ${ &gt;} $</annotation>\u0000 </semantics></math> 2 compared to <i>Kp</i> <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>≤</mo>\u0000 </mrow>\u0000 <annotation> $mathit{le }$</annotation>\u0000 </semantics></math> 2. The results of the latitudinal distribution characteristic of ULF waves in the Pc3-5 bands can contribute to further investigation on the estimation of 3-D radial diffusion coefficients.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144300467","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":"3-D MHD Stability of Magnetotail Configurations With a Bz Hump","authors":"J. Birn,&nbsp;V. G. Merkin,&nbsp;M. I. Sitnov,&nbsp;M. Hesse","doi":"10.1029/2024JA033648","DOIUrl":"https://doi.org/10.1029/2024JA033648","url":null,"abstract":"&lt;p&gt;Using three-dimensional ideal magnetohydrodynamics (MHD) simulations, we explore the stability of magnetotail configurations that include a local enhancement 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;B&lt;/mi&gt;\u0000 &lt;mi&gt;z&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${B}_{z}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; (a “&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;B&lt;/mi&gt;\u0000 &lt;mi&gt;z&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${B}_{z}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; hump”). We focus on configurations that were previously found to be unstable in 2-D (neglecting cross-tail, &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;y&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $y$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, variations as well as a cross-tail magnetic field component &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;B&lt;/mi&gt;\u0000 &lt;mi&gt;y&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${B}_{y}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;) but approached final 2-D stable states. Not surprisingly, the 2-D unstable configurations were also found unstable in 3-D, developing 3-D structure after an initial rise as in 2-D. This is consistent with the fact that the selected &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;B&lt;/mi&gt;\u0000 &lt;mi&gt;z&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${B}_{z}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; hump configurations are characterized also by a local tailward decrease of field line entropy, which has been found to govern ballooning/interchange (B/I) instability (Schindler &amp; Birn, 2004, https://10.1029/2004JA010537). The evolution of the electric field perturbation of the unstable 3-D modes showed an early exponential growth, which was only modestly faster than the 2-D mode. This might suggest that the unstable ballooning regime extends from &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;k&lt;/mi&gt;\u0000 &lt;mi&gt;y&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;mo&gt;→&lt;/mo&gt;\u0000 &lt;mi&gt;∞&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${k}_{y}to infty $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; (proper ballooning modes) over finite &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;k&lt;/mi&gt;\u0000 &lt;mi&gt;y&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${k}_{y","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144292850","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":"Overestimation of the Bottom-Side Ionospheric TEC in the IRI Model Over Low Latitude Regions","authors":"K. Venkatesh,&nbsp;H. Kava,&nbsp;D. Pallamraju,&nbsp;Gopi K. Seemala","doi":"10.1029/2025JA033827","DOIUrl":"https://doi.org/10.1029/2025JA033827","url":null,"abstract":"<p>It is known that the ionospheric Total Electron Content (TEC) variations estimated by the IRI model show large differences from observed values over the low latitudes. While studies on the topside ionospheric contributions to the errors in the modeled TEC by the IRI are under active consideration, there have been no studies on the role of the contribution of the bottom-side ionosphere. As ionosondes provide the true information on the bottom-side TEC, in this work a comparative study has been carried out in discerning the role of various parameters that go into the estimates of bottom-side density profiles and electron content in the IRI model (TECb_iri). The digisonde measurements over a low latitude location, Ahmedabad, India are used to estimate the bottom-side electron content (TECb_digi) during 2015 and 2018. It is found that the TECb_iri is overestimated during day time irrespective of the season and solar activity. The maximum differences in TECb_digi are noted during equinoctial months and high solar activity period. Among the F-layer peak and profile parameters, the model differences in the bottom-side thickness (<i>B0</i>) are found to be consistent with the differences in the TECb_iri. The agreements and discrepancies between TECb_iri and TECb_digi, under the influence of complex electrodynamic processes and solar flux are discussed. This study provides crucial information required to delineate the contributions of different empirical parameters in the IRI to address the discrepancies that exist in the bottom-side ionospheric modeling over low latitudes.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144281573","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":"Juno-Derived Electron Density Profiles of the High-Latitude Jovian Ionosphere","authors":"Drew A. Coffin,&nbsp;Paul Withers,&nbsp;Omakshi Agiwal,&nbsp;Dustin Buccino,&nbsp;Marzia Parisi,&nbsp;Ryan S. Caruso,&nbsp;Andrea Caruso,&nbsp;Luis Gomez Casajus,&nbsp;Edoardo Gramigna,&nbsp;Paolo Tortora,&nbsp;Marco Zannoni,&nbsp;Jack Hunter Waite,&nbsp;Paul Steffes,&nbsp;Sushil Atreya,&nbsp;Scott Bolton","doi":"10.1029/2025JA033754","DOIUrl":"https://doi.org/10.1029/2025JA033754","url":null,"abstract":"<p>The magnetosphere of Jupiter is an excellent natural laboratory for plasma dynamics due to its strength and internal plasma source. However, a complication in understanding the flow of energy through the system is the closure of the driving current systems within the chaotic high-latitude ionosphere of Jupiter, a region that has been poorly surveyed. The polar orbit of the Juno spacecraft permits for the first time multiple observations of the high- and mid-latitude ionosphere through the radio occultation technique. This paper presents derived electron density profiles from four such occultations. Seven profiles, four ingress and three egress, all sample the dawn limb but at a range of magnetic latitudes, including an ingress profile within <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msup>\u0000 <mn>5</mn>\u0000 <mi>o</mi>\u0000 </msup>\u0000 </mrow>\u0000 <annotation> ${5}^{o}$</annotation>\u0000 </semantics></math> of the main oval that is consistent with a response to high-energy electron influx. These profiles demonstrate variability in peak densities, peak altitude, and even the number of layers present. This high level of variability in Jupiter's high-latitude ionosphere suggests a complex network of current closure with high temporal variability.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144281424","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":"Modes of Daily Mean Thermospheric ΣO/N2 Variability Over a Solar Cycle Observed by TIMED/GUVI","authors":"C. E. Cantrall,&nbsp;Y. Zhang,&nbsp;L. J. Paxton,&nbsp;R. K. Schaefer","doi":"10.1029/2024JA033384","DOIUrl":"https://doi.org/10.1029/2024JA033384","url":null,"abstract":"<p>The relative column abundance of monatomic oxygen to molecular nitrogen (ΣO/N₂) in the lower thermosphere has been measured for over two decades by TIMED/GUVI. This data set provides an opportunity to assess how well current empirical thermosphere climatologies reproduce observed composition variations on timescales of days to a solar cycle. Here, we characterize and compare the primary modes of daily mean thermospheric ΣO/N₂ variability measured by TIMED/GUVI and generated from NRLMSIS 2.0 over a solar cycle from 2008 to 2019 using principal component analysis. The geophysical significance of these modes and their dependence on solar and geomagnetic drivers is further determined. We find that the ΣO/N₂ variability over this period observed by GUVI is dominated by three distinct modes; two associated with intra-annual variations, that is, the annual and semiannual oscillations (AO and SAO), and one associated with the response to geomagnetic activity. These three modes account for 88% of the total global variability over the time period; the AO accounts for 53%, the SAO accounts for 28%, and geomagnetic activity response accounts for 7%. The separation of the AO and SAO denotes unique spatial structures and driver modulation for each of these modes. NRLMSIS 2.0 shows strong agreement with GUVI for the geomagnetic activity mode. In contrast, the two modes associated with intra-annual variations displayed different spatial structures and dependencies on solar-geomagnetic conditions, particularly solar EUV radiative flux, compared to GUVI. These results highlight important discrepancies in intra-annual variations of composition in the lower thermosphere between the NRLMSIS climatology and long-term GUVI observations.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144281388","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":"Multi-Point Satellites Observed Dawnside Subauroral Polarization Streams (SAPS) Developed on a Short Timescale Under Weak-Storm and Non-Storm Substorm Conditions","authors":"Ildiko Horvath,&nbsp;Brian C. Lovell","doi":"10.1029/2025JA033755","DOIUrl":"https://doi.org/10.1029/2025JA033755","url":null,"abstract":"<p>We study the development of the magnetosphere-ionosphere (M-I) conjugate dawnside Subauroral Polarization Streams (SAPS) by investigating the newly-formed dawnside SAPS observed soon after dawnside substorm onset. Our topside-ionosphere results show that (a) the eastward dawnside SAPS flow was weaker than the eastward auroral return flow and (b) the equatorward and downward SAPS electric (E) field components were not accompanied by any dawnside upward Region-2 field-aligned currents. These provide observational evidence that (c) the substorm current wedge (SCW) developed on the dawnside and (d) the newly-formed dawnside SAPS observed developed in a voltage generator of magnetospheric origin. Our inner-magnetosphere results show (e) the charge separation at the dawnside plasmapause, where (f) the inward (earthward) SAPS E field developed in (g) a voltage generator, (h) on a short timescale, and (i) during localized particle injections (j) associated with the dawnside SCW. From these (a–j) new results we conclude that the M-I conjugate dawnside SAPS observed developed on a short timescale, in a magnetospheric voltage generator, of which root cause was the fast development of the dawnside SCW. Our conclusion is consistent with the fast-time development of the M-I conjugate duskside SAPS, of which root cause is the fast development of the duskside SCW.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA033755","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144281399","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}