Journal of Geophysical Research: Space Physics最新文献

{"title":"Neutrals Ejected From Io's Plasma/Atmosphere Interaction Region by Physical Chemistry Processes","authors":"V. Dols","doi":"10.1029/2025JA033798","DOIUrl":"https://doi.org/10.1029/2025JA033798","url":null,"abstract":"<p>Neutrals ejected from Io's atmosphere are the source of many important structures of the jovian magnetosphere: they feed giant neutral clouds, which extend along Io's orbit and nebulae, which extend beyond 500 jovian radii. The neutral loss rate is casually claimed to be ∼1 ton/s, but the processes leading to this loss, their quantitative estimates, and the speed and direction of the ejected neutrals are poorly constrained. In this study, we focus on neutrals ejected by physical chemistry processes resulting from the interaction of the torus plasma interacting with the atmosphere. These processes include electron-impact dissociative-ionization and dissociation, symmetrical and asymmetrical charge exchange and ion recombination. Our approach is based on a prescribed atmospheric distribution of SO₂, SO, S and O. We combine an MHD code to compute the plasma flow into the atmosphere and a Multi-Species Physical Chemistry code to compute the plasma properties (electrons, SO₂⁺, SO⁺, S⁺, S⁺⁺, S⁺⁺⁺, O⁺, O⁺⁺ densities and temperatures) and reaction rates along flowlines. In this article, we focus on reactions that specifically produce neutrals and compute their ejection rates, their velocity distribution and ejection direction. Using simplifying assumptions about the atmosphere, the flow and properties of the torus plasma, we provide an upper limit of the neutrals lost by physical chemistry processes ∼1 ton/s, with a velocity distribution specific for each reaction ranging from 0 to 120 km/s. The dominant processes are in the order of importance: molecular ion charge exchange, electron-impact dissociation and molecular ion dissociative-recombination, the last of which is prevalent in Io's wake.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 8","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA033798","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144905572","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":"A Numerical Study on the Responses of Thermosphere Density to the IMF \u0000 \u0000 \u0000 \u0000 B\u0000 y\u0000 \u0000 \u0000 ${B}_{y}$\u0000 Condition at High Latitudes","authors":"Yusha Tan,&nbsp;Jiuhou Lei,&nbsp;Zhongli Li,&nbsp;Xiaoli Luan,&nbsp;Xiankang Dou","doi":"10.1029/2025JA034113","DOIUrl":"https://doi.org/10.1029/2025JA034113","url":null,"abstract":"<p>When the Interplanetary magnetic field (IMF) <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>B</mi>\u0000 <mi>y</mi>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${B}_{y}$</annotation>\u0000 </semantics></math> condition disturbs, the ionospheric convection pattern is tilted, subsequently altering thermospheric dynamics. While both observations and simulations have shown that the thermospheric mass density exhibits significantly different patterns under positive and negative IMF <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>B</mi>\u0000 <mi>y</mi>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${B}_{y}$</annotation>\u0000 </semantics></math> conditions, the underlying mechanisms driving the density variations at different altitudes are not well-established. In this study, we investigate the physical mechanisms responsible for the density variations based on the Thermosphere Ionosphere Electrodynamics General Circulation Model simulations. The model simulations show strong consistency with observations and indicate that density variations have universal time dependence. Meanwhile, the density variations driven by IMF <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>B</mi>\u0000 <mi>y</mi>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${B}_{y}$</annotation>\u0000 </semantics></math> disturbance exhibit different mechanisms in the lower and upper thermosphere. In particular, at around 200 km, the effect of non-local thermal variations dominates density changes, where the altitude-integrated effect of neutral temperature changes at lower altitudes primarily drives mass density variations at higher altitudes. At around 400 km, the composition effect associated with local vertical wind becomes the dominant driver in changing the mass density.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 8","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144894283","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":"Seasonal Variation of Daytime Electron Density Irregularity Distributions in the Bottom and Top Sides of the Low Latitude F Region","authors":"Hoang Nguyen,&nbsp;Young-Sil Kwak,&nbsp;Hyosub Kil,&nbsp;Woo Kyoung Lee","doi":"10.1029/2025JA033902","DOIUrl":"https://doi.org/10.1029/2025JA033902","url":null,"abstract":"<p>The occurrence rate of daytime electron density irregularities in the low-latitude F region around the solar minimum exhibits different seasonal patterns in the Northern Asian sector (near 110°E longitude), depending on the data set used. This study examines this discrepancy using Beidou total electron content (TEC) data and vertical TEC profiles from the radio occultation experiment onboard the Constellation Observing System for Meteorology, and Ionosphere, and Climate (COSMIC) during the period 2017–2019. At the northern low latitudes near 110°E, the irregularity occurrence rate derived from Beidou TEC data is higher around the December solstice than around the June solstice. This seasonal behavior is opposite to that from the in situ satellite measurements on the topside. The irregularity distributions derived from COSMIC TEC profiles reveal altitudinal variations in seasonal occurrence patterns: the occurrence rate is higher around the December solstice than around the June solstice in the bottom side (150–250 km altitude) of the F region, whereas the seasonal pattern on the topside (450–700 km altitude) exhibits the opposite behavior. These seasonal patterns on the bottomside and topside are consistent with those derived from the Beidou TEC and in situ satellite measurements, respectively. These findings suggest that Beidou TEC perturbations during the daytime primarily represent irregularities on the bottom side. We interpret the altitudinal difference in the irregularity distribution as a result of differences in the sources of irregularities at different altitudes.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 8","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA033902","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144897355","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":"Upper Limit on Radiation Belt Electron Fluxes Controlled by a Self-Consistent Feedback From Chorus Waves","authors":"Ruoxian Zhou,&nbsp;Xiao-Jia Zhang,&nbsp;Didier Mourenas,&nbsp;Anton V. Artemyev","doi":"10.1029/2025JA034116","DOIUrl":"https://doi.org/10.1029/2025JA034116","url":null,"abstract":"<p>Electron fluxes vary widely in the Earth's outer radiation belt and represent an important hazard for satellites. Chorus waves are generated by anisotropic electrons and can accelerate or precipitate them into the atmosphere. Here, a Fokker-Planck diffusion code is used to approximately simulate the self-consistent evolution of both 0.03–1 MeV electron fluxes and chorus wave power, from initially low levels, during sustained low-energy electron injections from the plasma sheet. This evolution results from wave-driven quasi-linear pitch-angle, energy, and mixed electron diffusion, combined with wave power amplification through cyclotron resonance with electrons. A simple but reasonable proxy is used to model chorus wave growth in four separate frequency bands. Simulations demonstrate that after strong and sustained low-energy electron injections, 0.03–1 MeV electron fluxes stabilize at a self-consistent upper limit, close to the Kennel-Petschek limit. However, the exact shape in energy of this self-consistent upper limit corresponds to the steady-state attractor of the dynamical electron flux/wave power system in the presence of both pitch-angle and energy diffusion, self-consistently described by Fokker-Planck and linear chorus wave power gain equations. We show that the characteristics of this self-consistent upper limit weakly depend on initial parameters, and align well with Van Allen Probes observations.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 8","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144892477","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":"Impact of Solar Wind Density and Velocity on Martian Ion Escape: A Study Using the Dynamic Box Method","authors":"Guanchun Wei,&nbsp;Ming Wang,&nbsp;Jianyong Lu,&nbsp;Lianghai Xie,&nbsp;Jiaqi Zhang,&nbsp;Jinyu Li,&nbsp;Kehan Du,&nbsp;Mingming Zhan","doi":"10.1029/2025JA034260","DOIUrl":"https://doi.org/10.1029/2025JA034260","url":null,"abstract":"<p>Ion escape is a key mechanism driving the long-term atmospheric evolution of Mars, and variations in solar wind conditions significantly influence ion escape rates. However, the different responses of various ion species within plume and tailward escape channels under varying solar wind velocities and densities remain poorly understood, hindering a comprehensive understanding of Martian atmospheric loss processes. To address this issue, we employ a three-dimensional multifluid MHD model to systematically simulate the escape behaviors of three major heavy ion species (O⁺, O₂⁺, and CO₂⁺) under different solar wind conditions. We propose a novel dynamic channel separation method based on the location of the magnetic pile-up boundary, which enables an accurate distinction between plume and tailward escape regions. This approach allows for a more precise assessment of escape rates, channel contributions, and energy spectra by ion species. Simulation results show that: (a) the total escape rates of all three ions increase significantly with rising solar wind density and velocity, with tailward escape showing a steeper increase. (b) As solar wind density increases, O₂⁺ replaces O⁺ as the dominant escaping ion. Although CO₂⁺ exhibits the lowest total escape rate, it shows the highest sensitivity to solar wind variations. (c) Energy spectral analysis reveals clear differences between the two escape channels. Plume escape ions generally have higher energies, with O⁺ more energetic than O₂⁺ and CO₂⁺. In contrast, the energy of escaping ions shows a positive correlation with ion mass in the tailward escape channel.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 8","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144892481","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":"Observations and Fully Coupled Simulations of Nighttime Ionospheric Irregularities in the Subauroral E Region","authors":"D. L. Hysell,&nbsp;M. F. Larsen","doi":"10.1029/2025JA034247","DOIUrl":"https://doi.org/10.1029/2025JA034247","url":null,"abstract":"<p>Observations and theory of plasma density irregularities in subauroral sporadic <i>E</i> layers are presented. The irregularities produce so-called quasiperiodic (QP) coherent scatter radar echoes, and imagery of the echoes reveals large-scale structuring which normally takes the form of bands of backscatter elongated from northwest to southeast and propagating to the southwest in the northern hemisphere. We associate the large-scale structuring with neutral dynamics in general and Ekman-type instability in particular. This is an inflection point instability, a generalization of Kelvin-Helmholtz instability in turning shears, the same shears that form sporadic <i>E</i> ionization layers in the first place. A key parameter for the instability is <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>α</mi>\u0000 </mrow>\u0000 <annotation> $alpha $</annotation>\u0000 </semantics></math>, the asymptotic direction of the neutral winds at the top of the shear spiral relative to magnetic east. The <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>α</mi>\u0000 </mrow>\u0000 <annotation> $alpha $</annotation>\u0000 </semantics></math> parameter controls the alignment of the rolls produced by inflection point instability. Numerical simulations involving fully coupled neutral and ionospheric dynamics reproduce many of the characteristics of the QP echoes. We argue that only angles <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>α</mi>\u0000 </mrow>\u0000 <annotation> $alpha $</annotation>\u0000 </semantics></math> within the first two quadrants are consistent with sporadic <i>E</i> layer formation, and only angles in the second quadrant are consistent with the production of strong field-aligned currents which may be necessary for small-scale field-aligned plasma density irregularity creation. This may explain the alignment of QP-echo striations observed by imaging radar.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 8","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144892480","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":"Hiss Waves Near the South Atlantic Anomaly in the Inner Plasmasphere","authors":"Huicong Chen,&nbsp;Hui Zhu,&nbsp;Yingying Zhao,&nbsp;Zhijie Qin,&nbsp;Zhenghao She","doi":"10.1029/2025JA034266","DOIUrl":"https://doi.org/10.1029/2025JA034266","url":null,"abstract":"&lt;p&gt;Plasmaspheric hiss is an important electromagnetic wave with a broad frequency range from &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;∼&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${sim} $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;10 Hz to several kHz. In this study, we statistically investigate the distribution of the plasmaspheric hiss wave near the South Atlantic Anomaly (SAA) using data from the Van Allen Probes. We first detect power peaks of hiss waves with frequencies below &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;∼&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${sim} $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;600 Hz near the SAA in the &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;L&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $L$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;-shell region from &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;∼&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${sim} $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;1.1 to &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;∼&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${sim} $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;2.0. The results show stronger hiss wave power on the dayside and in boreal summer. For frequencies below &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;∼&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${sim} $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;300 Hz, power peaks are observed across the &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;L&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $L$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;-shell regions &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;1.1&lt;/mn&gt;\u0000 &lt;mo&gt;&lt;&lt;/mo&gt;\u0000 &lt;mi&gt;L&lt;/mi&gt;\u0000 &lt;mo&gt;&lt;&lt;/mo&gt;\u0000 &lt;mn&gt;2.0&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $1.1&lt; L&lt; 2.0$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, while for frequencies between &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;∼&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${sim} $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;300 Hz and &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;∼&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${sim} $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;600 Hz, these peaks become confined to lower &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;L&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $L$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;-shell regions &lt;span&gt;&lt;/span&gt;&lt;math","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 8","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144892479","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":"Distributions of Solar Wind Discontinuity Normals for Different Solar Activity and Solar Wind Types","authors":"S. H. Lee,&nbsp;D. G. Sibeck,&nbsp;D. R. Weimer,&nbsp;F. Koller,&nbsp;N. Omidi","doi":"10.1029/2025JA033945","DOIUrl":"https://doi.org/10.1029/2025JA033945","url":null,"abstract":"<p>We present a statistical analysis of the interplanetary magnetic field (IMF) discontinuity normals across solar cycle 23 and 24 for different solar wind types. We employ both the Minimum variance analysis (MVA) and Cross-product methods to determine phase front normals using ACE observations. We confirm that most discontinuity normals point earthward and dawnward at longitudes from 180<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <annotation> ${}^{circ}$</annotation>\u0000 </semantics></math> to 250<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <annotation> ${}^{circ}$</annotation>\u0000 </semantics></math> and lie between latitudes −40<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <annotation> ${}^{circ}$</annotation>\u0000 </semantics></math> and 40<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <annotation> ${}^{circ}$</annotation>\u0000 </semantics></math>. A wider range of normals is observed during the solar minimum and declining phases compared to the solar maximum and ascending phases. Discontinuities point strongly northward or southward more frequently during solar minimum than during solar maximum. We categorize the data into four solar wind types, Coronal Mass Ejections-Magnetic Ejecta (CME-ME), CME-SH (Sheath), Stream Interaction Regions (SIR), and Non-CME/Non-SIR for the years 2001–2002 (solar maximum) and 2008–2009 (solar minimum). The discontinuity normals are strongly oriented antisunward during CMEs (CME-MEs and CME-SHs). The distributions during SIRs are similar to those observed in the absence of any particular solar wind type.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 8","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144891770","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 Observations of Large-Scale Azimuthal Fields in Jupiter's Nightside Magnetosphere: Extended Analysis and Physical Implications","authors":"S. W. H. Cowley,&nbsp;G. Provan,&nbsp;J. D. Nichols","doi":"10.1029/2025JA033993","DOIUrl":"https://doi.org/10.1029/2025JA033993","url":null,"abstract":"<p>We study Jupiter's nightside magnetospheric azimuthal magnetic field using measurements from the first 58 data-taking periapsides of the Juno spacecraft, spanning post-dawn to pre-dusk local times (LTs). The methodology follows Provan et al. (2024, https://doi.org/10.1029/2024JA032677) but extends the analysis to 40 Jupiter radii distances, allowing better discrimination of field variations at dusk. The field has two components, (a) a field varying along field lines inversely with perpendicular distance from the magnetic axis, taken to be associated with magnetosphere-ionosphere coupling, and (b) a quasi-uniform field consistent with a field ∼4 nT pointing sunward/antisunward in the southern/northern hemisphere. These components are separated by subtracting the quasi-uniform field, yielding colatitude profiles of the ionospheric current versus LT from which the atmospheric torque on the magnetospheric plasma is calculated. Currents peak on outer magnetosphere field lines at ∼12.5 MA per radian of azimuth at dusk, falling to ∼6.5 MA rad⁻¹ at midnight but remain at ∼2 MA rad⁻¹ polar values at dawn. Corresponding outer magnetosphere torques are ∼1.1 × 10¹⁸ N m in the dusk-midnight quadrant, falling to ∼0.2 × 10¹⁸ N m in the midnight-dawn quadrant. The quasi-uniform field also provides a torque on the equatorial plasma, corotational in the midnight-dawn sector ∼0.6–0.8 × 10¹⁸ N m augmenting the atmospheric torque, but anti-corotational in the dusk sector opposing the atmospheric torque. We propose that the quasi-uniform fields and related ionospheric LT asymmetries are associated with the confinement of iogenic plasma outflow in the down-tail direction, possibly augmented by more direct interaction with the solar wind at the magnetopause.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 8","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA033993","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144881230","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":"Excitation of Mirror Mode Waves and Whistler Waves in Space Plasmas","authors":"Xudong Guo,&nbsp;Tieyan Wang,&nbsp;Jinsong Zhao,&nbsp;Chen Shi,&nbsp;Yuhang Yao,&nbsp;Xiangcheng Dong","doi":"10.1029/2025JA034084","DOIUrl":"https://doi.org/10.1029/2025JA034084","url":null,"abstract":"<p>Recent observations have revealed that mirror mode waves and whistler waves coexist in space plasmas containing multiple ion and electron components. This raises the question of which particle component is responsible for exciting each type of wave. Based on data from the Magnetospheric Multiscale mission, this paper investigates the excitation mechanisms of both mirror mode and whistler waves during a typical wave event in the Earth's magnetosheath. To characterize the observed magnetosheath environment, we employ a five-component plasma model that includes low- and high-energy electron components, low- and high-energy proton components, as well as one alpha particle component. Our theoretical instability analysis reveals that both mirror instability and whistler instability are excited locally. Moreover, we find that the unstable mirror mode waves absorb free energy from all proton and electron components exhibiting perpendicular temperature anisotropy. In contrast, the energy source for the unstable whistler waves is solely attributed to the high-energy electron component. These findings enhance our understanding of the complex energy transfer processes associated with multi-scale waves in space plasmas.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 8","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144881419","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}