空间等离子体中的动理学平衡态结构模型  

Kinetic models of equilibrium structures in space plasmas

作　　者：李京寰 杨帆 周煦之[1] Li Jinghuan;Yang Fan;Zhou Xuzhi(School of Earth and Space Sciences,Peking university,Beijing 100871,China)

机构地区：[1]北京大学地球与空间科学学院,北京100871

出　　处：《地球与行星物理论评》2022年第5期532-543,共12页Reviews of Geophysics and Planetary Physics

基　　金：国家自然科学基金资助项目(42174184)。

摘　　要：空间等离子体环境中存在着大量尺度不一的电磁结构,如电流片、磁洞、磁通量绳等,它们的尺度大至磁流体动力学尺度,小至离子甚至电子动理学尺度.随着卫星观测水平的提高,人们已对这些结构内的电磁场和粒子分布拥有了更多的认知,但仅借助观测本身仍难以完整描述它们的三维结构.因此,对这些结构开展理论和数值模拟研究极为重要.本文简要介绍了一种对空间电磁结构进行理论建模的通用框架,即从Vlasov-Maxwell方程出发构建动理学平衡态自洽解,再将其与卫星观测进行对比.近年来,这套方法已被广泛应用于对空间电磁结构的建模和重构,证实了动理学平衡态结构在空间中的大量存在.同时,这种方法也可以作为初始条件应用于结构演化的模拟.最后,本文指出了这一方法目前存在的问题,并提出了几个可能的发展方向.In the space plasma environments,there are a variety of electromagnetic structures,including current sheets,magnetic holes and flux ropes,for which scales range from fluid down to ion or even electron kinetic scales.Our understanding of these structures,especially their electromagnetic field profiles and particle distributions,has been greatly improved due to the recent improvement in spacecraft technologies and enhancement in the observational database.To fully achieve the three-dimensional configurations of these structures,it is insufficient to use only the observations but also the theoretical models and numerical simulations.This paper briefly reviews the general framework of constructing theoretical models over these structures,which are self-consistent equilibrium solutions of Vlasov-Maxwell equations.In this framework,to ensure the satisfaction of the equilibrium Vlasov equation,particle distribution is expressed as a function of the particle invariant's motion.The moments of the particle distributions are then substituted into the Maxwell equations to solve the profiles of electromagnetic fields,which are further used to determine the particle phase space densities that can be compared directly to spacecraft observations.In recent years,this framework has been widely applied in the modeling and reconstruction of electromagnetic structures,demonstrating the ubiquitous presence of kinetic equilibrium structures in space plasmas.Moreover,the self-consistent models can be used as initial conditions of kinetic simulations.Finally,we discuss the open questions and future directions in studying kinetic structures in space plasmas.

关 键 词：电磁结构 动理学平衡态 磁洞 磁通量绳 

分 类 号：P354[天文地球—空间物理学]