动力学阿尔文波及其在太阳和空间等离子体中的应用(英文)

KINETIC ALFVEN WAVES AND THEIR APPLICATIONS IN SOLAR AND SPACE PLASMAS

动力学阿尔文波是短波长的色散阿尔文波,其色散主要是由于垂直波长接近离子回旋半径或电子惯性长度等微观粒子动力学特征尺度而引起的。在频率远低于离子回旋频率的低频条件下,其平行波长通常仍然远大于离子惯性长度,这导致动力学阿尔文波在电磁偏振和传播方向上呈现显著各向异性的重要特性,并因此使其在磁等离子体的粒子能化现象和结构丝化现象中起重要作用。动力学阿尔文波早期于1970年代由Chen和Hasegawa研究聚变等离子体加热问题时首先提出。随后,在1980年代受到空间等离子体、特别是电离层-磁层耦合与极光现象研究的广泛关注。进入1990年代后,由于在空间卫星探测技术和地面等离子体实验技术的不断发展,特别是一些高分辨空间等离子体探测仪器和地面大型等离子体实验设备投入工作以来,在动力学阿尔文波的实验研究上取得了一系列突破性的重要进展。这不仅导致对动力学阿尔文波在磁等离子体动力学现象中重要作用的重新估价和正视,并再次激发了对动力学阿尔文波理论及其在实验室、空间和天体环境下各类等离子体活动现象中应用研究的广泛兴趣。自1990年代中期以来,我们在中国科学院紫金山天文台的研究小组一直致力于动力学阿尔文波及其在太阳和空间等离子体粒子能化现象中应用的研究。这篇综述性报告主要介绍了有关动力学阿尔文波非线性孤波理论及其在空间和太阳等离子体粒子能化现象中应用的研究进展,也是我们这十几年来在这一领域研究工作的一个总结。报告的第0章简要介绍动力学阿尔文波的一些主要特征及其在磁等离子体动力学现象中的重要作用。然后,在第1章中利用等离子体的双流体方程、结合有关的实验观测,系统介绍了动力学阿尔文波的色散、传播、偏振等基本特性和在一维孤波与二维涡旋等非线性结构理论方面的研究进展。接下来的第2、3、4章将聚焦在动力学阿尔文波的耗散机制及其在太阳和空间等离子体粒子能化现象中的应用研究上,分别包括:动力学阿尔文孤波的耗散结构及其在极光高能电子加速现象中的应用(第2章);动力学阿尔文孤波中重离子的各向异性能化机制及其在延伸日冕中少量重离子反常加热现象中的应用(第3章);以及动力学阿尔文波的反常耗散机制及其在日冕磁等离子体结构非均匀加热现象中的应用(第4章)。最后的第5章是一个简要的总结和几点进一步发展的展望。

Kinetic Alfven Waves （KAWs hereafter） are dispersive Alfven waves with a short perpendicular wavelength comparable to microscopic kinetic scales of particles, such as the ion gyroradius （or the ion-acoustic gyroradius） and the electron inertial length, but a parallel wavelength longer than the ion inertial length because of their low frequencies below the ion cyclotron frequency. Due to their anisotropic characteristics in the electromagnetic polarization and the propagation direction, KAWs can play an important role in the energization of particles and the formation of filamentous structures in magneto-plasmas. In 1970＇s, KAWs were proposed by Chen and Hasegawa in studies on the heating problem of fusion plasmas. Later, KAWs in space plasmas, especially their role in the magnetosphere-ionosphere coupling and the auroral plasma dynamics, were extensively discussed by many authors in 1980＇s. Since 1990＇s, advances in both space and ground-based plasma experimental techniques, in particular, high-resolution exploration in space plasma and large plasma device in laboratory becoming available, have lead to a series of great progresses in experimental study of KAWs. This leads to the reevaluation of the importance of KAWs in the dynamics of magneto-plasmas and remotivates studying interest of KAWs and their roles in various active phenomena from laboratory, space, to astrophysical plasmas. Since the middle of 1990＇s our group at Purple Mountain Observatory has devoted ourselves to the investigation of KAWs and their applications in dynamic phenomena of solar and space plasmas. In this paper we present a comprehensive review of KAWs and their applications, which is also a summary of our work in last more than ten years. We start with describing basic properties of KAWs and showing why KAWs are important in chapter 0. Then, based on the two-fluid equations of plasmas and the experimental observations, theories of dispersion, propagation, and polariation of KAWs and their nonlinear structures in the form of one-dimensional solitary waves and two-dimensional vortices are introduced in chapter 1. In the rest parts of this report, chapters 2, 3, and 4 will focus on dissipation mechanisms of KAWs and their applications in particle energization phenomena in solar and space plasmas, including the shock-like structure of dissipated solitary KAWs and its application in the acceleration of auroral energetic electrons （chapter 2）; the anisotropic energization mechanism of heavy ions in solitary KAWs and its application in anomalous energization phenomena of minor heavy ions in the extended solar corona （chapter 3）; and anomalous dissipation mechanisms of KAWs and their application in nonuniform heating phenomena of magneto-plasma structures in the solar atmosphere （chapter 4）. Finally, a brief summary and a few perspectives for open problems of KAWs are presented in chapter 5.