Journal of Geophysical Research: Space Physics最新文献

{"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}

{"title":"Propagation Characteristics of Lightning-Generated Whistlers in the Ionosphere: Statistical and Simulation-Based Analysis","authors":"Tian Xiang,&nbsp;Moran Liu,&nbsp;Shimin He,&nbsp;Xiang Xu,&nbsp;Shufan Zhao,&nbsp;Chen Zhou","doi":"10.1029/2024JA033546","DOIUrl":"https://doi.org/10.1029/2024JA033546","url":null,"abstract":"<p>Lightning-generated whistlers (LGWs) are electromagnetic waves in the very-low-frequency band generated by lightning and propagate in the ionosphere. LGWs are an inexpensive ionospheric detection medium that can be used to reconstruct ionospheric electron density based on their dispersion characteristics. The propagation characteristics of LGWs determine their propagation paths in the ionosphere, and the correct calculation of these paths is a prerequisite for electron density inversion. Here the observations from the China Seismo-Electromagnetic Satellite in broad areas at about 500 km altitude are used to perform wave vector direction statistics and propagation characteristics analysis for fractional-hop whistlers that propagate from the Earth to the spacecraft. The propagation characteristics of whistlers are analyzed and distinguished using observational statistics of wave vector directions and simulation based on the finite difference time domain model. The results indicate that the wave normal angles of whistlers in low latitudes are significantly larger than those in mid latitudes. Low-latitude whistlers preferentially propagate obliquely outward in the magnetic meridian plane in a nonducted mode in the ionosphere. Mid-latitude whistlers may still propagate in a nonducted mode, even when their wave normal angles are relatively small. The wave normal angles of LGWs in the ionosphere show no significant longitudinal dependence and exhibit a clear latitudinal distribution pattern. The LGWs wave vector exhibits minimal vertical deviation at low and high latitudes, with significantly larger deviations near 30°N mid-latitudes. This paper reveals the propagation characteristics of LGWs in the ionosphere through observations, statistics, and simulation.</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":"144281422","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":"Generation of UHR Waves as Inferred From Wave and Electron Flux Measurements by Van Allen Probes","authors":"D. R. Shklyar,&nbsp;E. E. Titova,&nbsp;N. S. Artekha","doi":"10.1029/2025JA033815","DOIUrl":"https://doi.org/10.1029/2025JA033815","url":null,"abstract":"<p>Observations of upper hybrid resonance (UHR) waves by Van Allen Probes show that the intensity of these waves increases significantly when their frequency is close to an integer multiple of electron gyrofrequency. This article aims at explaining these observations. The explanation assumes that the UHR waves are excited due to cyclotron instability at higher-order cyclotron resonances. Since UHR waves have relatively small group velocity, propagation effect should not play an important role in spectrum evolution of these waves. Thus, the spectrum observed at a given point should be closely related to the wave growth rate at the same point. We calculate the linear growth rate of UHR waves along Van Allen Probe trajectory using the registered plasma parameters and energetic electron density deduced from differential flux measurements. Apart from the hot plasma density, we use other parameters of model distribution compatible with but not inferred from flux measurements. The growth rate along the satellite trajectory calculated in this way fits well the simultaneous spectrum 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":"144281423","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 Role of Cold Oxygen Ions in the EMIC Wave Growth","authors":"Shujie Gu,&nbsp;Misa Cowee,&nbsp;Xiangrong Fu,&nbsp;Lunjin Chen,&nbsp;Xu Liu,&nbsp;Vania Jordanova","doi":"10.1029/2024JA033661","DOIUrl":"https://doi.org/10.1029/2024JA033661","url":null,"abstract":"<p>Electromagnetic ion cyclotron (EMIC) waves, driven by ring current ion temperature anisotropy in the Earth's magnetosphere, play a key role in accelerating and precipitating relativistic electrons in the radiation belts. Their excitation and saturation are significantly affected by the surrounding cold plasma. Previous studies have shown that background cold helium ions can influence the growth and saturation of EMIC waves, yet the role of cold oxygen ions in wave saturation remains less understood. In this paper, we use linear theory and nonlinear hybrid simulation to investigate the effect of cold oxygen ions in the EMIC wave growth and saturation in a homogeneous plasma containing hot and cold protons, cold helium and cold oxygen ions. Our findings reveal that increasing the cold oxygen ion concentration decreases the EMIC wave growth rate and broadens the spectral width of stop bands near the helium and oxygen gyrofrequencies. Furthermore, an increasing oxygen ion concentration notably reduces the saturation amplitude of EMIC waves in cases where the helium band is dominant, while cases with a dominant hydrogen band remain unaffected. Cold ions are heated during wave excitation, and cold helium ions are heated to keV energy, more significantly than cold protons and oxygen ions. With cold oxygen ion concentration increasing, cold helium ions take longer time to be heated to keV energy. These results offer insights into how cold plasma modifies the spectral properties and amplitudes of EMIC waves, shedding light on energy transfer from hot protons to cold plasma through EMIC waves.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144273170","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":"Control of Solar Wind on Magnetic Field Fluctuations in the Subsolar Magnetosheath","authors":"Ying Zou,&nbsp;Brian M. Walsh,&nbsp;Yuxi Chen,&nbsp;Hongyang Zhou,&nbsp;Savvas Raptis","doi":"10.1029/2025JA033856","DOIUrl":"https://doi.org/10.1029/2025JA033856","url":null,"abstract":"<p>The magnetosheath modifies the solar wind and IMF before they reach Earth's magnetosphere, and hence plays a crucial role in regulating the solar wind-magnetosphere interaction. Although the steady component of the magnetosheath magnetic field has been reasonably well reproduced, the fluctuating component has been less accounted for despite its significant amplitude. This paper empirically determines the mean characteristics of the ultra-low-frequency magnetic field fluctuations, and constructs a functional form using solar wind parameters. We use 15 years of THEMIS A data for the magnetosheath, and OMNI for the upstream solar wind conditions. Qualitatively, fluctuations are negatively correlated with the IMF cone angle, and positively with the solar wind speed and dynamic pressure. Some fluctuations are correlated with the IMF strength but not all. The level of fluctuations in the IMF is positively correlated with &lt;0.01 Hz fluctuations in the magnetosheath. A higher Mach number is associated with a larger fraction of compressional versus transverse fluctuations in the magnetosheath. Quantitatively, the correlation between magnetosheath fluctuations and individual solar wind parameters is weak, correlation magnitude being &lt;0.5. However, by performing a multiple linear regression fit of the solar wind parameters to magnetosheath fluctuations, a reasonably good prediction can be achieved with correlation magnitude in the range of 0.5–0.7, except for the parallel magnetosheath fluctuations of 0.01–0.1 Hz. Our results are overall consistent with earlier studies, but our quantitative approach further permits forecast of how much the IMF changes inside the magnetosheath which is beneficial for scientific understanding and space weather forecasts.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144264655","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}