光学天文与技术应用研究室知识库

电子回旋脉泽辐射是一种重要的射电辐射机制,将其应用在太阳物理中,需要解决两个困难:一是自由能来源问题;二是辐射的逃逸问题。高能电子束离开加速区后,在磁等离子体中与磁场、波等相互作用可以形成不同的速度空间分布,可以为脉泽辐射提供自由能。对于辐射逃逸问题,日冕低密度导管的假设可以解决这一困难。介绍了近几年回旋脉泽辐射研究的进展及其在太阳射电爆发中的应用,以及阐述了该领域未来研究方向。

Electron-cyclotron maser (ECM) emission is a well-known radiation emission mechanism in astrophysics. It has been extensively applied to various nonthermal coherent radio emission, especially to the short-timescale coherent radio bursts. Excitation of electron cyclotron maser radiation requires two basic conditions. One is the inversion distribution of the energetic electrons in the direction perpendicular to the ambient magnetic field. The other is the escape difficulty that requires the local electron cyclotron frequency over the plasma frequency. These two conditions are hardly satisfied in the corona under the conventional solar atmosphere models, which limit the application of ECM emission mechanism to solar radio astronomy. In general, flare associated energetic electrons are accelerated initially mainly along the magnetic field, it means that these energetic electrons do not have enough free energy to drive ECM emission. After the energetic electrons leave the acceleration site and propagate in the solar atmosphere, the energy of the energetic electrons in the parallel orientation can be transfer to the perpendicular orientation, and form an anisotropic distribution due to the interaction of energetic electrons with magnetic field and plasma waves. For the escape difficulty, a density depletion duct in the corona is necessary and may be rational as optical observations show fibrous density structures exist commonly in the corona. This paper presents a systematic review on the recent development of ECM emission mechanism, especially on the new models which may overcome the above difficulties and can be applied in several kinds of solar radio bursts, such as type I bursts, type II bursts, and type V bursts. Some perspectives on the study of ECM mechanism and solar radio emission processes are also presented.