Journal of Geophysical Research: Space Physics最新文献

{"title":"Ionospheric Vertical Correlation Analysis and Modeling Using COSMIC-2 Global Ionospheric Specification Data","authors":"Shuo Liu,&nbsp;Tao Yu,&nbsp;Xiangxiang Yan,&nbsp;Yan Yu,&nbsp;Yu Liang,&nbsp;Kezhi Huang,&nbsp;Yifan Qi","doi":"10.1029/2025JA034008","DOIUrl":"https://doi.org/10.1029/2025JA034008","url":null,"abstract":"<p>The background error covariance matrix is essential in ionospheric data assimilation, enabling the integration of observational data with model predictions by defining spatial relationships between grid points. The vertical component plays a key role in enhancing model accuracy by capturing altitude-dependent spatial correlations, directly influencing electron density profile reconstruction. In this study, we used Constellation Observing System for Meteorology, Ionosphere, and Climate-2 Global Ionospheric Specification data to analyze vertical correlation distances in the ionosphere, identifying the altitude range where the correlation coefficient exceeds 0.75 in both upward and downward directions. The results revealed a clear pattern: vertical correlation distances initially increased with altitude, then the rate of increase slowed or decreased before rising again. Significant variations were observed with local time (LT), geomagnetic latitude, and seasonal effects. Winter anomalies, possibly due to changes in the O/N₂ ratio, amplified vertical correlations, particularly between LT 12:00 and 18:00. A layered Gaussian model was developed to parameterize the vertical correlation coefficients, and its accuracy and adaptability were validated across different seasonal conditions. The model's correlation with observational data was greater than 0.75 across all seasons, with relatively small errors at lower altitudes, typically within 50 km. At reference heights exceeding 500 km, the error range remained within approximately 100 km for most points. These findings contribute to the development of more accurate ionospheric models, which are essential for satellite communication, navigation, and space weather forecasting.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144197288","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 Nonlinear Interactions Between Chorus and Electron Cyclotron Harmonic Waves","authors":"Lixian Yang,&nbsp;Si Liu,&nbsp;Zhonglei Gao,&nbsp;Hongming Yang,&nbsp;Xiongjun Shang,&nbsp;Yang Gao,&nbsp;Fuliang Xiao","doi":"10.1029/2025JA034027","DOIUrl":"https://doi.org/10.1029/2025JA034027","url":null,"abstract":"&lt;p&gt;Nonlinear wave-wave interactions are crucial for extending wave frequency ranges and redistributing energy, thereby influencing the magnetospheric dynamics. The interactions between chorus and electron cyclotron harmonic (ECH) waves can generate the ECH sidebands. Statistical analysis of Van Allen Probes data shows that these interactions primarily occur in the region of &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; = 5.0&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;–&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $mbox{--}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;6.0 and MLT = 23&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;–&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $mbox{--}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;09 near the equator &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;mo&gt;|&lt;/mo&gt;\u0000 &lt;mi&gt;M&lt;/mi&gt;\u0000 &lt;mi&gt;L&lt;/mi&gt;\u0000 &lt;mi&gt;A&lt;/mi&gt;\u0000 &lt;mi&gt;T&lt;/mi&gt;\u0000 &lt;mo&gt;|&lt;/mo&gt;\u0000 &lt;mo&gt;&lt;&lt;/mo&gt;\u0000 &lt;mn&gt;5&lt;/mn&gt;\u0000 &lt;mo&gt;°&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;mo&gt;)&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $(vert mathrm{M}mathrm{L}mathrm{A}mathrm{T}vert &lt; 5{}^{circ})$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;. As the AE index increases, the ECH sidebands occur over a wider region and their intensity grows. Moreover, the root-mean-square (RMS) amplitude of the ECH sideband &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mfenced&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;E&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;S&lt;/mi&gt;\u0000 &lt;mo&gt;-&lt;/mo&gt;\u0000 &lt;mtext&gt;RMS&lt;/mtext&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mfenced&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $left({E}_{mathrm{S}mbox{-}text{RMS}}right)$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; is roughly in proportion to the square root of the product of that of the chorus &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mfenced&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;E&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;C&lt;/mi&gt;\u0000 &lt;mo&gt;-&lt;/mo&gt;\u0000 &lt;mtext&gt;RMS&lt;/mtext&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mfenced&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $left({E}_{mathrm{C}mbox{-}text{RMS}}right)$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; and ECH &lt;span&gt;&lt;/span&gt;&lt;math&gt;","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144179012","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 Observations in Support of Bow Shock Current Closure to Earth's High-Latitude Ionosphere During Non-Zero IMF By","authors":"G. Nordin,&nbsp;M. Hamrin,&nbsp;E. Krämer,&nbsp;P. Dredger,&nbsp;S. Fatemi,&nbsp;R. E. Lopez,&nbsp;S. E. Milan,&nbsp;T. Pitkänen,&nbsp;T. Karlsson,&nbsp;O. Goncharov","doi":"10.1029/2024JA033599","DOIUrl":"https://doi.org/10.1029/2024JA033599","url":null,"abstract":"&lt;p&gt;The bow shock current (BSC) plays an important role in supplying the magnetosphere with solar wind energy, in particular during times of low solar wind magnetosonic Mach numbers. Since the magnetic pile-up in the magnetosheath has to be maintained, the BSC cannot close locally, but must instead connect to magnetospheric current systems. However, the details of this closure remain poorly understood. For east–west interplanetary magnetic field (IMF) it has been hypothesized that the BSC partly closes to the high-latitude ionosphere, as field-aligned currents (FACs) on open field lines, but there is still no statistical evidence of this. In order to investigate this hypothesis, we use 9 years of Defense Meteorological Satellite Program (DMSP) data to construct normalized FAC maps of the northern hemisphere polar cap. We sort them according to different IMF clock angles, IMF magnitudes and magnetosonic Mach numbers. By separating opposite polarity FACs, we show that, on average, a unipolar FAC exists in the dayside polar cap when the IMF &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;mo&gt;≠&lt;/mo&gt;\u0000 &lt;mn&gt;0&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${B}_{y}ne 0$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, regardless of the sign of the IMF &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;. This current flows out of (into) the ionosphere in the northern hemisphere for IMF &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;mo&gt;&gt;&lt;/mo&gt;\u0000 &lt;mn&gt;0&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${B}_{y} &gt; 0$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; &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;mo&gt;&lt;&lt;/mo&gt;\u0000 &lt;mn&gt;0&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;mo&gt;)&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $(&lt; 0)$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; and is thus of the correct polarity to connect to the north–south component of the BSC. Moreover, it is strongest when the BSC flows predominantly in the north–south direction. These results constitute the first statistical evidence in support of at least a partial closure of the BSC to the ionosphere during non-zero IMF &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;se","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA033599","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144179293","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":"Concurrence and Coupling of EMIC and EFH Instabilities in the Hot Electron Plasma","authors":"Zhiqiang Wang,&nbsp;Jiacheng Zhong,&nbsp;Erkang Zhang,&nbsp;Yufei Li","doi":"10.1029/2024JA033702","DOIUrl":"https://doi.org/10.1029/2024JA033702","url":null,"abstract":"&lt;p&gt;Kinetic instabilities play an important role in the dynamics of the magnetospheric system. Generally, electrons are deemed to be unrelated to the generation of electromagnetic ion cyclotron (EMIC) waves. In this work, a parameter study is performed on the EMIC instability affected by parallel anisotropic electrons (&lt;i&gt;A&lt;/i&gt;&lt;i&gt;&lt;sub&gt;e&lt;/sub&gt;&lt;/i&gt; &lt; 1) in the inner magnetosphere. The wave dispersion relation and wave growth rate are calculated by a numerical method (named PDRK/BO). The plasma instabilities are analyzed and compared by using different combination of parameters (electron temperature, anisotropy and proportion). With the increase of hot electron proportion (&lt;i&gt;N&lt;/i&gt;&lt;i&gt;&lt;sub&gt;e&lt;/sub&gt;&lt;/i&gt;), waves are found to grow successively at &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;ω&lt;/mi&gt;\u0000 &lt;mo&gt;&gt;&lt;/mo&gt;\u0000 &lt;mn&gt;0.5&lt;/mn&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;Ω&lt;/mi&gt;\u0000 &lt;mi&gt;H&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $omega &gt; 0.5{{Omega }}_{H}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; and &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;ω&lt;/mi&gt;\u0000 &lt;mo&gt;&gt;&lt;/mo&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;Ω&lt;/mi&gt;\u0000 &lt;mi&gt;H&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $omega &gt; {{Omega }}_{H}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;. The minimum electron energies for cyclotron resonance with EMIC waves indicate that the unusual hydrogen band waves at &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;ω&lt;/mi&gt;\u0000 &lt;mo&gt;&gt;&lt;/mo&gt;\u0000 &lt;mn&gt;0.5&lt;/mn&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;Ω&lt;/mi&gt;\u0000 &lt;mi&gt;H&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $omega &gt; 0.5{{Omega }}_{H}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; are relevant to the electron resonance mechanism. This is different from the normal hydrogen band waves at &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;ω&lt;/mi&gt;\u0000 &lt;mo&gt;&lt;&lt;/mo&gt;\u0000 &lt;mn&gt;0.5&lt;/mn&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;Ω&lt;/mi&gt;\u0000 &lt;mi&gt;H&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $omega &lt; 0.5{{Omega }}_{H}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, which are the ion resonance mode in nature. The electron firehose (EFH) modes are excited by the parallel anisotropic electrons. Due to the wave couplings between EMIC and EFH modes, the dispersion relations of EMIC waves are changed significantly, and the frequencies at peak growth rates of EMIC waves are moved regularly with the increase of &lt;i&gt;N&lt;/i&gt;&lt;i&gt;&lt;sub&gt;e&lt;/sub&gt;&lt;/i&gt;. Our studies suggest that the energy transfer between electrons and ions h","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144171919","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":"Global Survey of Whistler-Mode Waves in the Lunar Plasma Environment: Insights From 11 Years of ARTEMIS Observations","authors":"Abhinav Prasad,&nbsp;Wen Li,&nbsp;Qianli Ma,&nbsp;Xiao-Chen Shen,&nbsp;Anton Artemyev,&nbsp;Andrew R. Poppe,&nbsp;Yuki Harada,&nbsp;Murong Qin,&nbsp;Vassilis Angelopoulos,&nbsp;Mei-Yun Lin","doi":"10.1029/2025JA033820","DOIUrl":"https://doi.org/10.1029/2025JA033820","url":null,"abstract":"<p>Whistler-mode waves are among the most ubiquitously observed plasma waves in the vicinity of Earth's Moon, providing an important diagnostic tool for plasma processes. However, a complete understanding of key plasma parameters responsible for whistler-mode generation remains elusive. In this study, we conduct a comprehensive statistical survey using 11 years of in-situ measurements from the ARTEMIS mission to reveal the global distribution of whistler-mode wave amplitude and occurrence rate as the Moon traverses through the solar wind, magnetosheath, and magnetotail during a typical lunar orbit. Our findings reveal that the highest whistler-mode wave amplitudes are observed when the Moon crosses Earth's magnetosheath. A parametric study is conducted to explore the correlation between whistler-mode wave occurrence rate and plasma parameters such as electron temperature anisotropy and heat flux. These parameters are analyzed separately for low-energy (&lt;100 eV) and high-energy (&gt;100 eV) electrons. The results indicate that whistler-mode wave occurrence rates exhibit a stronger positive correlation with the temperature anisotropy of high-energy electrons compared to low-energy electrons. Moreover, the parallel heat flux (normalized by the free streaming heat flux) of high-energy electrons shows a moderate positive correlation with whistler-mode wave amplitude (normalized to the background magnetic field) in both the solar wind and magnetosheath regions. We further investigate the influence of the background magnetic field line connection to the lunar surface on whistler-mode waves. Overall, our analysis demonstrates that the temperature anisotropy of high-energy electrons has a higher positive correlation with magnetic field connection than that of low-energy electrons.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144171920","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 Study on the Connections Between TEC Periodic Disturbances Associated With MSTIDs and Mid-Latitude Frequency Spread F in Summer Nights Over China","authors":"Ke Li,&nbsp;Donghe Zhang,&nbsp;Yaoyu Tian,&nbsp;Shuji Sun,&nbsp;Hongyu Gao,&nbsp;Yi Zeng,&nbsp;Guanglin Yang,&nbsp;Yongqiang Hao","doi":"10.1029/2025JA033706","DOIUrl":"https://doi.org/10.1029/2025JA033706","url":null,"abstract":"<p>In this study, the connections between medium-scale traveling ionospheric disturbances (MSTIDs) and mid-latitude frequency spread F (FSF) during summer nights in the China sector are statistically investigated using data from over 250 GNSS stations and 12 ionosonde stations from 2014 to 2018. First, both phenomena are observed to commonly occur on the same night during summer, with longer durations of FSF corresponding to higher average MSTIDs activity values. MSTIDs activity tends to precede the FSF occurrence. The statistical peak distribution of MSTIDs activity is concentrated before midnight, whereas FSF peaks after midnight, with median occurrence time differing by approximately 1–2 hr. Additionally, FSF and MSTIDs exhibit similar spatial propagation characteristics, with occurrences in the northeastern region occurring earlier in universal time (UT). Building on these findings, the potential physical processes and mechanisms by which MSTIDs may excite FSF are further discussed, including the role of E-F coupling, as well as significant changes in critical frequency and virtual height at different MSTIDs activity conditions. Furthermore, the underlying reasons for the differences in the temporal distribution of FSF at different latitudes are also analyzed. The midnight type FSF may be related to the disturbed electric fields in MSTIDs and gradient drift instability, while presunrise type FSF mainly concentrates at higher latitudes, without obvious connections to MSTID activity, suggesting the existence of excitation mechanisms beyond MSTIDs.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144179066","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":"Small-Scale Magnetic Flux Rope Structures Across the Earth's Bow Shock","authors":"Rebecca Harvey,&nbsp;Qiang Hu,&nbsp;Yu Chen","doi":"10.1029/2025JA033897","DOIUrl":"https://doi.org/10.1029/2025JA033897","url":null,"abstract":"<p>This work identifies and characterizes magnetic structures, especially in terms of small-scale magnetic flux ropes (SFRs), in the solar wind and magnetosheath across the Earth's bow shock. We investigate the differences between the properties of SFR structures in these regions immediately upstream and downstream of the bow shock by employing two data analysis methods: one based on wavelet transforms and the other based on the Grad-Shafranov (GS) detection and reconstruction techniques. In situ magnetic field and plasma data from the Magnetospheric Multiscale and Time History of Events and Macroscale Interactions during Substorms missions are used to identify these coherent structures through the two approaches. We identify thousands of SFR event intervals with a range of variable duration over a total time period of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>≲</mo>\u0000 </mrow>\u0000 <annotation> $lesssim $</annotation>\u0000 </semantics></math>1,000 hr in each region. We report parameters associated with the SFRs such as scale size, duration, magnetic flux content, and magnetic helicity density, derived from primarily the GS-based analysis results. These parameters are summarized through statistical analysis, and their changes across the bow shock are shown based on comparisons of their respective distributions. We find that in general, the distributions of various parameters follow power laws. The SFR structures seem to be compressed in the magnetosheath, as compared with their counterparts in the solar wind. A significant rotation in the <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>z</mi>\u0000 </mrow>\u0000 <annotation> $z$</annotation>\u0000 </semantics></math>-axis defining the orientation of the structures is also seen across the bow shock. We also discuss the implications for the elongation of the SFRs in the magnetosheath along one spatial dimension.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144171918","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":"Identifying Magnetotail Jet Front Signatures in a 3D + 3V Global Hybrid-Vlasov Simulation","authors":"L. Pänkäläinen,&nbsp;G. Cozzani,&nbsp;M. Battarbee,&nbsp;U. Ganse,&nbsp;Y. Pfau-Kempf,&nbsp;J. Suni,&nbsp;M. Palmroth","doi":"10.1029/2025JA033892","DOIUrl":"https://doi.org/10.1029/2025JA033892","url":null,"abstract":"<p>Magnetic reconnection in Earth's magnetotail is thought to create bursty bulk flows (BBFs), short-lived plasma bulk velocity enhancements in the magnetotail's central plasma sheet (CPS) region. Closely related to BBFs are dipolarization fronts (DFs), sudden increases in <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mrow>\u0000 <msub>\u0000 <mi>B</mi>\u0000 <mi>z</mi>\u0000 </msub>\u0000 </mrow>\u0000 </mrow>\u0000 <annotation> ${B}_{z}$</annotation>\u0000 </semantics></math>, the magnetic field component aligned with Earth's magnetic dipole axis. BBFs are involved in, for example, transport of energy and mass, and DFs contribute to for instance energy conversion processes and plasma acceleration. Both phenomena increase magnetic flux transport in the magnetotail. We demonstrate novel methods of identifying BBFs and DFs in 3D global magnetospheric simulations and present results for multiple case studies. We search for BBFs and DFs in a simulation conducted using the 3D global magnetospheric hybrid-Vlasov code Vlasiator. DFs are identified using a <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mrow>\u0000 <msub>\u0000 <mi>B</mi>\u0000 <mi>z</mi>\u0000 </msub>\u0000 </mrow>\u0000 </mrow>\u0000 <annotation> ${B}_{z}$</annotation>\u0000 </semantics></math> time derivative threshold, whereas BBFs are defined based on a velocity threshold. The tailward DF (anti-DF) identification criteria are fulfilled by tailward-propagating flux ropes, while earthward-propagating DFs are mostly seen in finger-like structures of high earthward bulk velocity alongside BBFs. We show that detections of fast flows meeting the BBF criteria in virtual spacecraft time series also originate due to moving reconnection locations and movement of the current sheet within the CPS region, while the reconnection outflow stays roughly constant. The results show that rapid <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mrow>\u0000 <msub>\u0000 <mi>B</mi>\u0000 <mi>z</mi>\u0000 </msub>\u0000 </mrow>\u0000 </mrow>\u0000 <annotation> ${B}_{z}$</annotation>\u0000 </semantics></math> variations in the simulation have multiple sources, and similar satellite measurements of BBFs can arise from different physical phenomena. Our findings may help with interpreting satellite observations in the magnetotail.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA033892","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144171921","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":"Different Responses of O-Mode and X-Mode in Ionograms to Medium Scale Traveling Ionospheric Disturbances: Observations and Simulations","authors":"Qi Jiang,&nbsp;Jiuhou Lei,&nbsp;Guozhu Li,&nbsp;Fuqing Huang","doi":"10.1029/2025JA033762","DOIUrl":"https://doi.org/10.1029/2025JA033762","url":null,"abstract":"<p>U-shaped structures (or transient cusp-shaped features) are special phenomena in ionograms, related to the electron density perturbations in the ionospheric F region. However, the mechanisms that trigger distinct shape structures, such as U-shaped and hook-shaped ones, are not fully understood yet. In this study, the ray tracing method is utilized to simulate the synthesized ionograms over Sanya under the medium-scale traveling ionospheric disturbances (MSTIDs) whose propagation parameters are extracted from total electron content observations of BeiDou geostationary (GEO) satellites. It was illustrated that the simulated ionograms are generally consistent with the observations from Sanya ionosonde. Interestingly, X-mode radio waves exhibited stronger responses to MSTIDs, especially at lower frequencies. It was found that the multiple reflection of ionosonde radio wave among different MSTID wavefronts could be the primary cause of the U-shaped structures. The different responses between O-mode and X-mode are influenced by the angles between the geomagnetic field and the MSTID propagation direction. The O-mode (X-mode) traces become more prominent when the geomagnetic field is parallel (perpendicular) to the MSTID propagation direction. Additionally, the MSTID parameters can significantly influence the morphology of MSTID-induced structures in ionograms. For instance, an increase in relative amplitude of MSTID can cause the echo trace structures in ionograms to transform from U-shaped to hook-shaped. Moreover, the downward movement durations of these structures are modulated by the periods and vertical wavelengths of MSTID.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144148443","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 Long-Term Survey of the Role of Atmospheric Planetary Waves in the Day-to-Day Variability of the Ionosphere","authors":"Oluwafisayo P. Owolabi,&nbsp;Scott L. England,&nbsp;Guiping Liu","doi":"10.1029/2024JA033160","DOIUrl":"https://doi.org/10.1029/2024JA033160","url":null,"abstract":"<p>Atmospheric planetary waves play an important role in shaping how the ionosphere is coupled to the rest of the Earth's atmosphere. Of significant interest in this study are the 2-, 3-, and 6-day planetary waves. Using multiple long-term datasets, we performed an extensive survey of these wave events in the atmosphere and ionosphere. Our results show that 3-day (80%) and 6-day (92%) oscillations in the ionosphere observed from the ground have a known driver that originated mostly from a planetary wave, but 2-day oscillations often do not. While some of the 2- and 3-day ionospheric oscillations are associated with random fluctuations from the sun or magnetosphere, almost none of the 6-day oscillations in the ionosphere are associated with these external drivers. For the 2-day oscillations, there is a significant change in the correspondence between the ionospheric oscillation and known drivers during solstices (69%) compared to equinoxes (36%). The impact of the external drivers on 2-day oscillations in the ionosphere during equinoxes is ∼2 times larger than during solstices. When generating a corresponding response in the ionosphere, the strength of the amplitudes of 2-day westward wavenumber-3 planetary waves made a clear impact, but less clear for 3-day eastward 1 and 6-day eastward/westward planetary waves, revealing that wave amplitude is significant for driving ionospheric response. There is a likelihood of a 3-day eastward 1/6-day eastward planetary wave event generating a corresponding response in the ionosphere to be more when the solar activity conditions are low compared to when it is high.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA033160","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144148406","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}