磁场重联是宇宙中普遍存在的等离子体过程,是多种天体物理现象中爆发性能量释放的关键机制.它能够将储存的磁场能量快速转化为粒子的动能和热能,同时改变磁场拓扑结构.与地球不同,火星没有全球性的内禀磁层,而是具有局部的岩石圈磁场,...磁场重联是宇宙中普遍存在的等离子体过程,是多种天体物理现象中爆发性能量释放的关键机制.它能够将储存的磁场能量快速转化为粒子的动能和热能,同时改变磁场拓扑结构.与地球不同,火星没有全球性的内禀磁层,而是具有局部的岩石圈磁场,特别是在南半球的磁场较强.这种结构使得太阳风可以直接与火星电离层相互作用,通过质量装载和离子拾取等过程,形成包括弓激波、磁鞘、感应磁层顶和磁尾等结构的感应磁层.行星际磁场(interplanetary magnetic field,IMF)能够轻易穿透较弱的火星电离层,而岩石圈磁场可延伸至高空,形成类似于太阳日冕的复杂磁场拓扑,为磁场重联的发生创造了理想条件.此外,火星电离层中存在多种离子成分(如O_(2)^(+)、O^(+)和CO_(2)^(+)),并且某些区域的碰撞效应使得重联事件表现出与传统无碰撞质子-电子重联模型显著不同的特性.本文全面回顾了火星空间环境中磁场重联的观测、理论和数值模拟研究进展,重点分析了感应磁层顶/电离层顶、电离层内部、磁尾和磁鞘等关键区域的重联现象.来自火星大气与挥发分演化任务(the Mars Atmosphere and Volatile EvolutioN,MAVEN)和天问一号等探测任务的观测揭示了多样化的重联特征,包括Hall磁场、高速离子喷流、离子加热和拓扑变化.例如,在感应磁层顶,拖曳的行星际磁场与固定的电离层磁场重联产生朝向太阳的喷流,驱动显著的离子逃逸,局部逃逸率高达1.0×10^(24) s^(-1).在磁尾,重联事件多发生在太阳风对流电场为负(-E)的半球,表现出与质量相关的离子流出,并导致氧离子的突发逃逸,逃逸率可暂时达到全球水平,如2.4×10^(24) s^(-1).在电离层内部,特别是在强岩石圈磁场区域,开放-开放或拖曳-闭合磁力线之间的重联产生局部加速,并促成环间重联和电子通量增强等现象.本文的重点是磁场重联引发的电离层物质抛射(ionospheric mass ejection,IME),这是一种新发现的现象,类似于太阳的日冕物质抛射(CME).在电离层的低β区域,反向开放磁力线之间的重联会抛射出等离子体空腔,其密度下降数个数量级,伴随的流出速度超过火星的逃逸速度(约5 km/s).MAVEN数据分析表明,IME事件大约每火星日发生三次,每次抛射约1.3 kg的氧离子,累计约42亿年来造成相当于0.046 mm全球水层的氧损失.虽然在当前条件下这一贡献看似较小,但在早期太阳系中,太阳风密度和磁场较强时,大气侵蚀效应可能显著增强.在理论方面,本文介绍了适用于多离子成分重联的多流体广义欧姆定律,扩展了传统的双流体模型.通过无量纲化方法,推导了重离子和轻离子的惯性长度,揭示了分步解耦过程形成的多尺度扩散区,改变了Hall效应、流出结构和无量纲重联率.利用等效质量解释了与质子-电子模型相比的惯性尺度偏差,重离子因受轻离子向外电场影响而具有较大尺度.本文还讨论了碰撞效应,低高度(<300 km)区域的碰撞会展宽扩散区并降低重联效率,可能导致部分碰撞状态,涉及离子-中性或离子-离子相互作用.这些研究不仅阐明了驱动火星大气和水逃逸的能量转换机制,这是火星气候演化和宜居性的关键因素,还推动了基础重联理论的发展.未来,MAVEN与天问一号的多点协同观测,以及与太阳日冕物理的类比,将为这一等离子体过程的天然实验室提供更深入的见解.展开更多
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
文摘磁场重联是宇宙中普遍存在的等离子体过程,是多种天体物理现象中爆发性能量释放的关键机制.它能够将储存的磁场能量快速转化为粒子的动能和热能,同时改变磁场拓扑结构.与地球不同,火星没有全球性的内禀磁层,而是具有局部的岩石圈磁场,特别是在南半球的磁场较强.这种结构使得太阳风可以直接与火星电离层相互作用,通过质量装载和离子拾取等过程,形成包括弓激波、磁鞘、感应磁层顶和磁尾等结构的感应磁层.行星际磁场(interplanetary magnetic field,IMF)能够轻易穿透较弱的火星电离层,而岩石圈磁场可延伸至高空,形成类似于太阳日冕的复杂磁场拓扑,为磁场重联的发生创造了理想条件.此外,火星电离层中存在多种离子成分(如O_(2)^(+)、O^(+)和CO_(2)^(+)),并且某些区域的碰撞效应使得重联事件表现出与传统无碰撞质子-电子重联模型显著不同的特性.本文全面回顾了火星空间环境中磁场重联的观测、理论和数值模拟研究进展,重点分析了感应磁层顶/电离层顶、电离层内部、磁尾和磁鞘等关键区域的重联现象.来自火星大气与挥发分演化任务(the Mars Atmosphere and Volatile EvolutioN,MAVEN)和天问一号等探测任务的观测揭示了多样化的重联特征,包括Hall磁场、高速离子喷流、离子加热和拓扑变化.例如,在感应磁层顶,拖曳的行星际磁场与固定的电离层磁场重联产生朝向太阳的喷流,驱动显著的离子逃逸,局部逃逸率高达1.0×10^(24) s^(-1).在磁尾,重联事件多发生在太阳风对流电场为负(-E)的半球,表现出与质量相关的离子流出,并导致氧离子的突发逃逸,逃逸率可暂时达到全球水平,如2.4×10^(24) s^(-1).在电离层内部,特别是在强岩石圈磁场区域,开放-开放或拖曳-闭合磁力线之间的重联产生局部加速,并促成环间重联和电子通量增强等现象.本文的重点是磁场重联引发的电离层物质抛射(ionospheric mass ejection,IME),这是一种新发现的现象,类似于太阳的日冕物质抛射(CME).在电离层的低β区域,反向开放磁力线之间的重联会抛射出等离子体空腔,其密度下降数个数量级,伴随的流出速度超过火星的逃逸速度(约5 km/s).MAVEN数据分析表明,IME事件大约每火星日发生三次,每次抛射约1.3 kg的氧离子,累计约42亿年来造成相当于0.046 mm全球水层的氧损失.虽然在当前条件下这一贡献看似较小,但在早期太阳系中,太阳风密度和磁场较强时,大气侵蚀效应可能显著增强.在理论方面,本文介绍了适用于多离子成分重联的多流体广义欧姆定律,扩展了传统的双流体模型.通过无量纲化方法,推导了重离子和轻离子的惯性长度,揭示了分步解耦过程形成的多尺度扩散区,改变了Hall效应、流出结构和无量纲重联率.利用等效质量解释了与质子-电子模型相比的惯性尺度偏差,重离子因受轻离子向外电场影响而具有较大尺度.本文还讨论了碰撞效应,低高度(<300 km)区域的碰撞会展宽扩散区并降低重联效率,可能导致部分碰撞状态,涉及离子-中性或离子-离子相互作用.这些研究不仅阐明了驱动火星大气和水逃逸的能量转换机制,这是火星气候演化和宜居性的关键因素,还推动了基础重联理论的发展.未来,MAVEN与天问一号的多点协同观测,以及与太阳日冕物理的类比,将为这一等离子体过程的天然实验室提供更深入的见解.
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.
