太阳大气中束流-回流系统的动力学

The Dynamics of Beam-return Current Systems in the Solar Atmosphere

高能带电粒子束是各类天体活动现象中最常见的产物之一,它们在宇宙等离子体中传播的动力学,特别是基于电荷中性与电流中性(净余电流为零,即Inet=0)的要求而伴随的回流以及束流–回流系统的动力学,一直是天体物理研究中受到广泛关注的基本问题之一。近年来,太阳活动现象的多波段高分辨率观测及太阳风和地球电离层的高分辨率观测为人们深入研究这一问题提供了丰富的观测资料和细致的理论依据,并已经取得了一系列重要进展。在简要回顾太阳大气中束流–回流系统动力学的研究历史后,再对这一研究领域近年来的最新进展进行综合评述,内容包括回流及其成因的理论模型,束流-回流系统中的不稳定性,以及近来在数值模拟研究和观测分析研究方面的最新成果。同时,也对该领域的未来发展趋势和前景进行了简要讨论。

Beams of energetic charged particles are a common product from a variety of astrophysical activities. These beams may be naturally accompanied by return currents to maintain charge neutrality and zero-current. Their propagation in cosmic plasmas in general, and the dynamics of the beam-return current system in particular, have been under intensive investigation as a fundamental problem in astrophysics. On the other hand, the multi-wavelength, high-resolution observations of solar activities, observations of the solar wind and of Earth＇s ionosphere that have been routinely made recently offer a rich set of data on which theoretical studies can be built. After briefly reviewing the historical development of the investigations into the dynamics of the beam-return current system in a solar atmosphere, we present an overview of the recent developments in the theories on how the return current is generated, in examining the instabilities such a system may be subjected to, and in the numerical simulations as well as data analyses of such a system. We conclude by pointing out some possible directions that are worth pursuing in this field.