• ISSN 2097-1893
  • CN 10-1855/P
任杰,宗秋刚. 2022. 地球磁层中超低频波与低能粒子的相互作用. 地球与行星物理论评,53(4):432-442. doi: 10.19975/j.dqyxx.2022-005
引用本文: 任杰,宗秋刚. 2022. 地球磁层中超低频波与低能粒子的相互作用. 地球与行星物理论评,53(4):432-442. doi: 10.19975/j.dqyxx.2022-005
Ren J, Zong Q G. 2022. The interactions between ULF waves and cold charged particles in the Earth's magnetosphere. Reviews of Geophysics and Planetary Physics, 53(4): 432-442. doi: 10.19975/j.dqyxx.2022-005
Citation: Ren J, Zong Q G. 2022. The interactions between ULF waves and cold charged particles in the Earth's magnetosphere. Reviews of Geophysics and Planetary Physics, 53(4): 432-442. doi: 10.19975/j.dqyxx.2022-005

地球磁层中超低频波与低能粒子的相互作用

The interactions between ULF waves and cold charged particles in the Earth's magnetosphere

  • 摘要: 太阳风—磁层耦合过程会产生各种等离子体波,其中超低频波的频率最低(1 mHz~1 Hz)、波长最长(与内磁层磁力线长度相当)、能量密度最大. 超低频波在磁层粒子加速、物质输运和能量转化中起着重要作用. 以往的研究主要关注超低频波的全球性传播和分布特征以及这些波动与磁层能量粒子(辐射带电子和环电流离子)的相互作用过程. 最近几年人们逐渐发现超低频波与低能粒子之间相互作用对磁层动力学过程会产生重要影响. 本文主要综述了以下几个方面的研究进展,包括:(1)多卫星联合观测、多地面台站联合观测、辐射带能量电子的“回旋镖形”投掷角色散特征都证明存在局域性的超低频波,理论和观测表明这类超低频波的存在跟等离子体层羽状结构有关;(2)多卫星观测证明存在等离子体层顶表面波,并且发现“锯齿形”极光的形成跟等离子体层顶表面波有着密切联系;(3)理论和卫星观测表明超低频波可以通过漂移—弹跳共振加速等离子体层低能电子,通过 E × B 调制作用实现对低能离子成分的区分. 最后,本文还总结了超低频波与低能粒子相互作用对磁层动力学过程造成的可能影响,并展望了本研究方向亟待解决的问题.

     

    Abstract: In the solar wind-magnetosphere coupling processes, many kinds of plasma waves can be excited in the Earth's magnetosphere including ULF waves, hiss waves, chorus waves, etc. Among these waves, ULF waves are featured by the lowest wave frequency (1 mHz~1 Hz), the longest wavelength (comparable with the magnetic field line in the inner magnetosphere) and the highest wave power density. ULF waves can propagate along the geomagnetic field lines into the ionosphere and cause the joule heating of the ionosphere. Besides, after excited at the magnetopause, they can propagate earthward across the geomagnetic field lines and generate the standing Alfvén waves (poloidal mode and toroidal mode) via the field line resonance. The electric field component of the poloidal mode standing is aligned with the drift direction of charged particles trapped in the magnetosphere, allowing a strong interaction between ULF waves and particles. Therefore, ULF waves play a crucial role in the particle energization, mass transportation and energy transfer within the magnetosphere. Previous studies focus on the global propagation and distribution of ULF waves, and their interactions with energetic particles such as radiation belt electrons and ring current ions. Recent studies within 5 years shed new light on the localized ULF waves and the interactions between ULF waves and cold plasmaspheric particles, which are reviewed in this paper. The existence of the localized ULF waves has been verified in different ways including multi-spacecraft observations, coordinated ground station measurements and "boomerang-shaped" pitch angle features of resonant radiation belt electrons. Studies suggested that the localized ULF waves are probably associated with the plasmaspheric plume structure, which can generate the Alfvén speed barriers. Multi-spacecraft observations have demonstrated that there are plasmaspause surface waves, which modulate particle populations and different waves around the plasmapause, and cause the formation of the sawtooth aurora. The acceleration of cold electrons by ULF waves via drift-bounce resonance has been found based on the observations of electron's pitch angle features and energy spectrum, theoretical analyses and statistical studies. Cold ions can be energized and modulated by ULF waves via E × B , which can be used to distinguish ion species and study ions with energies out of the scope of instrument. In the final, we summarize the possible roles of the ULF wave-cold particle interactions in the dynamics of magnetosphere and list some important issues for future studies.

     

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