太阳微波爆发元过程的观测和理论研究

Enormous observations show that a powerful solar microwave burst always consists of a series of microwave pulses or pulse clusters with different timescales, and forms complicated fine structures. The physical processes related to these elementary cells of the complicated fine structures can be regarded as solar micorwave elementary processes (MEP). From the solar radio broadband spectral obsevations with high cadence and high spectral resolutions, parameters associated with these MEPs can be obtained, such as frequency bandwidth, frequency drfiting rate, harmonics, polarization degree, duration, and periodicity, etc. From the solar radio imaging observations at the corresponding frequencies, the spatial properties can also be obtained. With the study of these observable parameters, we can deduce the physical informations of the microwave source region, such as temperature, magnetic field, plasma density, and the kenematic properties, etc. This program plans to apply the observational data of the Chinese Solar Broadband Radio Spectrometer and the new generation Chinese Spectral Radioheliograph, also including other telescopes with multi-wavelength in the world, to study the solar microwave bursts. In particular, by using the combination of case-by-case investigation and statistic analysis, we will mainly focus on discoverying the new phenomena associated to the solar MEPs with shortest timescales, revealing the new physical rules of the triggering mechanisms of solar eruptive events, the primary energy release, and the particle accelerations associated to the source regions. This study can improve the development of nonlinear plasmas physics.

太阳微波观测表明，一个大爆发过程常常由一系列具有不同时标的脉冲或脉冲群构成，形成复杂的精细结构，与这些精细结构基本单元（即一个脉冲）对应的物理过程，为太阳微波爆发元过程。微波爆发元过程可以通过对射电宽带动态频谱图上的带宽、频漂率、谐波结构、偏振率、脉冲时间、周期性等参数的提取，获得有关辐射源区温度、磁场、等离子体密度、动力学特征等信息；通过成像观测还能得到其空间形态特征。本次研究计划利用我国太阳射电宽带动态频谱仪和即将建成的新一代中国射电频谱日像仪的观测数据，结合其它多波段观测资料，通过个例分析和统计研究相结合，寻找与具有最短时标的太阳微波爆发元过程有关的新现象，揭示在太阳爆发源区与爆发的触发机制、初始能量释放机制和粒子加速机制有关的新规律，并带动非线性等离子体物理的研究。

本项目重点研究了太阳微波元爆发、微波III型爆源区诊断、微波斑马纹的成因、耀斑前兆等问题。发现太阳耀斑过程中存在大量微波小爆发，断它们与耀斑源区大量小尺度磁场重联和粒子加速有关，是太阳爆发中的基元过程，很可能就是太阳耀斑中的元爆发；利用完全MHD方程，导出了一组新的关于微波III型爆源区磁场强度B、等离子体密度密度ne及其特征长度Hn、温度T、比压值、超热电子能量Eb等参数的诊断方程；在一个X级耀斑初始时刻发现斑马纹型的非热强爆发，推断在耀斑初始时刻的一个小尺度源区可能首先发生了磁重联，加速电子并对附近等离子体迅速加热；对太阳第24活动周的耀斑进行统计分析，发现在大多数强耀斑爆发之前的软X射线辐射存在周期为10-30分钟、持续时间1-2小时的甚长周期脉动结构，为理解耀斑触发机制并进行大耀斑的预报提供了重要信息；提出磁场梯度抽运机制解释日冕加热过程，为这一世纪难题的解决提供了一个新的理论途径。发表研究论文35篇，其中SCI/SSCI论文30篇，国际会议文集7篇，中文文章2篇；在国内外学术会议上提交报告21个，其中，特邀报告3个、口头报告16个、张贴报告2个；组织和参与组织国际学术会议5个、国内学术会议3个。发表论文被引用117次。