交换不稳定性广泛存在于工程和自然界中,被认为是木星磁盘内径向物质输运的主要机制之一.本文基于理想磁流体力学理论,考虑了木星内磁层基本物理参数(Feng et al.,2025),获得了未考虑局域近似(扰动波长远小于特征长度)条件下的木星内磁...交换不稳定性广泛存在于工程和自然界中,被认为是木星磁盘内径向物质输运的主要机制之一.本文基于理想磁流体力学理论,考虑了木星内磁层基本物理参数(Feng et al.,2025),获得了未考虑局域近似(扰动波长远小于特征长度)条件下的木星内磁层交换不稳定性色散关系和不稳定判据;通过理论分析获得了木星内磁层交换不稳定性的主要增长模式与增长率.分析结果显示,在当前的参数条件下,在木卫一环内侧区域交换模式稳定;在木卫一环外侧存在交换模式不稳定区间,理论给出了不稳定性发生的空间位置.结果还表明,在木卫一环外侧的离心力与密度梯度共同驱动了交换不稳定性,而偶极磁场曲率与熵梯度对交换模式起致稳作用.当环向模数小于10时,交换不稳定性增长率随环向模数增大而增长;当环向模数大于10时,增长率趋于饱和.交换不稳定性增长率随径向模数增大而减小.理论分析获得的主导模式与数值模拟中增长率最大模式的环向模数(环向模数为m=13)接近.与文献Newcomb(1961)和Ferrière等(1999)的理论结果对比显示,本文推导获得的理论结果与Ferrière理论模型的不稳定区域基本一致,但是与Newcomb理论模型给出的木卫一外侧全区域不稳定的结果有差异.上述差异主要是因为Newcomb理论模型采用平板构型,未考虑弯曲磁场曲率制稳的影响.对比分析显示,理论结果获得的交换不稳定性主导模式(环向模数13)的增长率与Ferrière理论模型增长率接近,这说明局域近似理论能较好地描述木星内磁层交换不稳定性增长过程.与数值模拟结果相比,理论分析获得的主导模式增长率偏高约一个量级.展开更多
This paper highlights the crucial role of Indonesia’s GNSS receiver network in advancing Equatorial Plasma Bubble(EPB)studies in Southeast and East Asia,as ionospheric irregularities within EPB can disrupt GNSS signa...This paper highlights the crucial role of Indonesia’s GNSS receiver network in advancing Equatorial Plasma Bubble(EPB)studies in Southeast and East Asia,as ionospheric irregularities within EPB can disrupt GNSS signals and degrade positioning accuracy.Managed by the Indonesian Geospatial Information Agency(BIG),the Indonesia Continuously Operating Reference Station(Ina-CORS)network comprises over 300 GNSS receivers spanning equatorial to southern low-latitude regions.Ina-CORS is uniquely situated to monitor EPB generation,zonal drift,and dissipation across Southeast Asia.We provide a practical tool for EPB research,by sharing two-dimensional rate of Total Electron Content(TEC)change index(ROTI)derived from this network.We generate ROTI maps with a 10-minute resolution,and samples from May 2024 are publicly available for further scientific research.Two preliminary findings from the ROTI maps of Ina-CORS are noteworthy.First,the Ina-CORS ROTI maps reveal that the irregularities within a broader EPB structure persist longer,increasing the potential for these irregularities to migrate farther eastward.Second,we demonstrate that combined ROTI maps from Ina-CORS and GNSS receivers in East Asia and Australia can be used to monitor the development of ionospheric irregularities in Southeast and East Asia.We have demonstrated the combined ROTI maps to capture the development of ionospheric irregularities in the Southeast/East Asian sector during the G5 Geomagnetic Storm on May 11,2024.We observed simultaneous ionospheric irregularities in Japan and Australia,respectively propagating northwestward and southwestward,before midnight,whereas Southeast Asia’s equatorial and low-latitude regions exhibited irregularities post-midnight.By sharing ROTI maps from Indonesia and integrating them with regional GNSS networks,researchers can conduct comprehensive EPB studies,enhancing the understanding of EPB behavior across Southeast and East Asia and contributing significantly to ionospheric research.展开更多
Theoretical analysis has demonstrated that the dispersion relation of chorus waves plays an essential role in the resonant interaction and energy transformation between the waves and magnetospheric electrons.Previous ...Theoretical analysis has demonstrated that the dispersion relation of chorus waves plays an essential role in the resonant interaction and energy transformation between the waves and magnetospheric electrons.Previous quantitative analyses often simplified the chorus dispersion relation by using the cold plasma assumption.However,the applicability of the cold plasma assumption is doubtful,especially during geomagnetic disturbances.We here present a systematic statistical analysis on the validity of the cold plasma dispersion relation of chorus waves based on observations from the Van Allen Probes over the period from 2012 to 2018.The statistical results show that the observed magnetic field intensities deviate substantially from those calculated from the cold plasma dispersion relation and that they become more pronounced with an increase in geomagnetic activity or a decrease in background plasma density.The region with large deviations is mainly concentrated in the nightside and expands in both the radial and azimuthal directions as the geomagnetic activity increases or the background plasma density decreases.In addition,the bounce-averaged electron scattering rates are computed by using the observed and cold plasma dispersion relation of chorus waves.Compared with usage of the cold plasma dispersion relation,usage of the observed dispersion relation considerably lowers the minimum resonant energy of electrons and lowers the scattering rates of electrons above tens of kiloelectronvolts but enhances those below.Furthermore,these differences are more pronounced with the enhancement of geomagnetic activity or the decrease in background plasma density.展开更多
The formation of an embedded electron current sheet within the magnetotail plasma sheet has been poorly understood.In this article,we present an electron current layer detected at the edge of the magnetotail plasma sh...The formation of an embedded electron current sheet within the magnetotail plasma sheet has been poorly understood.In this article,we present an electron current layer detected at the edge of the magnetotail plasma sheet.The ions were demagnetized inside the electron current layer,but the electrons were still frozen in with the magnetic field line.Thus,this decoupling of ions and electrons gave rise to a strong Hall electric field,which could be the reason for the formation of the embedded thin current layer.The magnetized electrons,the absence of the nongyrotropic electron distribution,and negligible energy dissipation in the layer indicate that magnetic reconnection had not been triggered within the embedded thin current layer.The highly asymmetric plasma on the two sides of the current layer and low magnetic shear across it could suppress magnetic reconnection.The observations indicate that the embedded electric current layer,probably generated by the Hall electric field,even down to electron scale,is not a sufficient condition for magnetic reconnection.展开更多
地球磁层顶频发的开尔文–赫姆霍兹(Kelvin-Helmholtz,K-H)不稳定性在太阳风的物质和能量向地球磁层的输运过程中发挥着重要的作用.研究筛选出2015-2020年中磁尾区域(X≈–60 Re)的磁层顶穿越事件,结合51个中磁尾处的K-H不稳定性事件,...地球磁层顶频发的开尔文–赫姆霍兹(Kelvin-Helmholtz,K-H)不稳定性在太阳风的物质和能量向地球磁层的输运过程中发挥着重要的作用.研究筛选出2015-2020年中磁尾区域(X≈–60 Re)的磁层顶穿越事件,结合51个中磁尾处的K-H不稳定性事件,统计研究了K-H不稳定性在中磁尾磁层顶的晨昏不对称性分布.结果表明,在中磁尾区域,磁层顶晨侧的K-H不稳定性发生率较高.在行星际磁场(Interplanetary Magnetic Field,IMF)北向条件下,发生在磁层顶晨侧的K-H不稳定性事件数量明显超越昏侧;当帕克–螺旋(Parker-Spiral,PS)IMF主导时,昏侧K-H不稳定性事件更多.太阳风的不同参数也会显著影响中磁尾区域磁层顶晨昏两侧的KH涡旋分布.磁尾区域的K-H波动也是导致磁尾等离子体片中不同温度的等离子体分布不对称的原因之一.展开更多
文摘交换不稳定性广泛存在于工程和自然界中,被认为是木星磁盘内径向物质输运的主要机制之一.本文基于理想磁流体力学理论,考虑了木星内磁层基本物理参数(Feng et al.,2025),获得了未考虑局域近似(扰动波长远小于特征长度)条件下的木星内磁层交换不稳定性色散关系和不稳定判据;通过理论分析获得了木星内磁层交换不稳定性的主要增长模式与增长率.分析结果显示,在当前的参数条件下,在木卫一环内侧区域交换模式稳定;在木卫一环外侧存在交换模式不稳定区间,理论给出了不稳定性发生的空间位置.结果还表明,在木卫一环外侧的离心力与密度梯度共同驱动了交换不稳定性,而偶极磁场曲率与熵梯度对交换模式起致稳作用.当环向模数小于10时,交换不稳定性增长率随环向模数增大而增长;当环向模数大于10时,增长率趋于饱和.交换不稳定性增长率随径向模数增大而减小.理论分析获得的主导模式与数值模拟中增长率最大模式的环向模数(环向模数为m=13)接近.与文献Newcomb(1961)和Ferrière等(1999)的理论结果对比显示,本文推导获得的理论结果与Ferrière理论模型的不稳定区域基本一致,但是与Newcomb理论模型给出的木卫一外侧全区域不稳定的结果有差异.上述差异主要是因为Newcomb理论模型采用平板构型,未考虑弯曲磁场曲率制稳的影响.对比分析显示,理论结果获得的交换不稳定性主导模式(环向模数13)的增长率与Ferrière理论模型增长率接近,这说明局域近似理论能较好地描述木星内磁层交换不稳定性增长过程.与数值模拟结果相比,理论分析获得的主导模式增长率偏高约一个量级.
基金JSPS KAKENHI Grant Number16H06286 supports global GNSS ionospheric maps (TEC,ROTI,and detrended TEC maps) developed by the Institute for SpaceEarth Environmental Research (ISEE) of Nagoya Universitysupport of the 2024 JASSO Follow-up Research Fellowship Program for a 90-day visiting research at the Institute for Space-Earth Environmental Research (ISEE),Nagoya University+3 种基金the support received from Telkom University under the“Skema Penelitian Terapan Periode I Tahun Anggaran 2024”the Memorandum of Understanding for Research Collaboration on Regional Ionospheric Observation (No:092/SAM3/TE-DEK/2021)the National Institute of Information and Communications Technology (NICT) International Exchange Program 2024-2025(No.2024-007)support for a one-year visiting research at Hokkaido University
文摘This paper highlights the crucial role of Indonesia’s GNSS receiver network in advancing Equatorial Plasma Bubble(EPB)studies in Southeast and East Asia,as ionospheric irregularities within EPB can disrupt GNSS signals and degrade positioning accuracy.Managed by the Indonesian Geospatial Information Agency(BIG),the Indonesia Continuously Operating Reference Station(Ina-CORS)network comprises over 300 GNSS receivers spanning equatorial to southern low-latitude regions.Ina-CORS is uniquely situated to monitor EPB generation,zonal drift,and dissipation across Southeast Asia.We provide a practical tool for EPB research,by sharing two-dimensional rate of Total Electron Content(TEC)change index(ROTI)derived from this network.We generate ROTI maps with a 10-minute resolution,and samples from May 2024 are publicly available for further scientific research.Two preliminary findings from the ROTI maps of Ina-CORS are noteworthy.First,the Ina-CORS ROTI maps reveal that the irregularities within a broader EPB structure persist longer,increasing the potential for these irregularities to migrate farther eastward.Second,we demonstrate that combined ROTI maps from Ina-CORS and GNSS receivers in East Asia and Australia can be used to monitor the development of ionospheric irregularities in Southeast and East Asia.We have demonstrated the combined ROTI maps to capture the development of ionospheric irregularities in the Southeast/East Asian sector during the G5 Geomagnetic Storm on May 11,2024.We observed simultaneous ionospheric irregularities in Japan and Australia,respectively propagating northwestward and southwestward,before midnight,whereas Southeast Asia’s equatorial and low-latitude regions exhibited irregularities post-midnight.By sharing ROTI maps from Indonesia and integrating them with regional GNSS networks,researchers can conduct comprehensive EPB studies,enhancing the understanding of EPB behavior across Southeast and East Asia and contributing significantly to ionospheric research.
基金supported by the National Natural Science Foundation of China (NSFC) through Grant Number 42074193
文摘Theoretical analysis has demonstrated that the dispersion relation of chorus waves plays an essential role in the resonant interaction and energy transformation between the waves and magnetospheric electrons.Previous quantitative analyses often simplified the chorus dispersion relation by using the cold plasma assumption.However,the applicability of the cold plasma assumption is doubtful,especially during geomagnetic disturbances.We here present a systematic statistical analysis on the validity of the cold plasma dispersion relation of chorus waves based on observations from the Van Allen Probes over the period from 2012 to 2018.The statistical results show that the observed magnetic field intensities deviate substantially from those calculated from the cold plasma dispersion relation and that they become more pronounced with an increase in geomagnetic activity or a decrease in background plasma density.The region with large deviations is mainly concentrated in the nightside and expands in both the radial and azimuthal directions as the geomagnetic activity increases or the background plasma density decreases.In addition,the bounce-averaged electron scattering rates are computed by using the observed and cold plasma dispersion relation of chorus waves.Compared with usage of the cold plasma dispersion relation,usage of the observed dispersion relation considerably lowers the minimum resonant energy of electrons and lowers the scattering rates of electrons above tens of kiloelectronvolts but enhances those below.Furthermore,these differences are more pronounced with the enhancement of geomagnetic activity or the decrease in background plasma density.
基金the National Natural Science Founda-tion of China(NSFC,Grant No.42174181)and the Key Research Program of Frontier Sciences,CAS(Grant No.QYZDJ-SSW-DQC010).
文摘The formation of an embedded electron current sheet within the magnetotail plasma sheet has been poorly understood.In this article,we present an electron current layer detected at the edge of the magnetotail plasma sheet.The ions were demagnetized inside the electron current layer,but the electrons were still frozen in with the magnetic field line.Thus,this decoupling of ions and electrons gave rise to a strong Hall electric field,which could be the reason for the formation of the embedded thin current layer.The magnetized electrons,the absence of the nongyrotropic electron distribution,and negligible energy dissipation in the layer indicate that magnetic reconnection had not been triggered within the embedded thin current layer.The highly asymmetric plasma on the two sides of the current layer and low magnetic shear across it could suppress magnetic reconnection.The observations indicate that the embedded electric current layer,probably generated by the Hall electric field,even down to electron scale,is not a sufficient condition for magnetic reconnection.
文摘地球磁层顶频发的开尔文–赫姆霍兹(Kelvin-Helmholtz,K-H)不稳定性在太阳风的物质和能量向地球磁层的输运过程中发挥着重要的作用.研究筛选出2015-2020年中磁尾区域(X≈–60 Re)的磁层顶穿越事件,结合51个中磁尾处的K-H不稳定性事件,统计研究了K-H不稳定性在中磁尾磁层顶的晨昏不对称性分布.结果表明,在中磁尾区域,磁层顶晨侧的K-H不稳定性发生率较高.在行星际磁场(Interplanetary Magnetic Field,IMF)北向条件下,发生在磁层顶晨侧的K-H不稳定性事件数量明显超越昏侧;当帕克–螺旋(Parker-Spiral,PS)IMF主导时,昏侧K-H不稳定性事件更多.太阳风的不同参数也会显著影响中磁尾区域磁层顶晨昏两侧的KH涡旋分布.磁尾区域的K-H波动也是导致磁尾等离子体片中不同温度的等离子体分布不对称的原因之一.
