日冕物质抛射热力学的多元磁流体模型研究

Studies on Coronal Mass Ejections (CMEs) are becoming increasingly important in space physics. Even though it has been widely accepted that the ultimate energy that drives CMEs derives from magnetic fields, it remains subjected to hot debate as to how the dissipated magnetic energy is partitioned among the kinetic, gravitational potential, and thermal energies. Such a partition may have significant influence on the propagation and evolution of CMEs, and hence on their space weather effects. From the perspective of the dynamic and thermodynamic evolution of CMEs, the observational fact that the electrons and protons are out of thermal equilibrium substantially complicates the already difficult situation. We will construct two-fluid Magnetohydrodynamic models of CMEs explicitly distinguishing between the electron and proton temperatures, thereby investigating, in a unified and self-consistent way, into the initiation, acceleration and propagation of CMEs. We will conduct time-dependent ionization balance computations to derive the charge state of various elements commonly measured in situ. By tracking the dynamic and thermodynamic evolution of CMEs from their source regions out to the Earth orbit, we will reach a deeper understanding, both theoretically and empirically, of how CMEs are heated. We will also be able to clarify the reliability of the empirical CME heating rates currently derived under the assumption that the electrons and protons are well coupled. We will elucidate, at least partially, how the in situ measurements of charge states can constrain the way electrons and protons respond to heating mechanisms like turbulence, Joule heating, and shocks. We will be able to shed light on the initiation mechanisms of CMEs by investigating into the constraints imposed on such mechanisms by charge state and Ultraviolet emission line measurements.

日冕物质抛射(CME)的研究日益成为空间物理学领域的焦点。虽然CME能源来自磁场这一点已有共识，但磁能在动能、引力势能及热能间如何分配仍无定论，这一分配可影响CME的传播与演化，从而影响其空间天气学效应。对CME热力学演化研究来说，电子与质子无法维持热平衡这一观测事实使问题更为棘手。本项目将构建明确区分电子、质子温度的CME的电子-质子两元磁流体模型，由此对CME的初发、加速、传播过程进行统一而自洽的研究；将发展基于最新原子物理数据的时变电离平衡计算工具，从而获得两元模型对应的痕量元素的电荷态以与观测对比。将通过追踪CME由源区直至1AU的动力学及热力学演化，深化CME加热的理论与经验认识；明确已有研究中未区分电子与质子温度情况下所得CME经验加热率之可靠性；部分阐明电荷态测量如何约束电子与质子对湍动、焦耳加热、激波等能量耗散方式的响应；并初步探讨电荷态及紫外测量对CME触发机制的约束。

研究将“日冕物质抛射的动力学及热力学”这一框架拆解为有着有机联系的若干层面，从理论模型、数值模拟和资料分析的角度开展了多角度研究。一、爆发热力学的实测研究：对爆发热力学演化做了细致分析，发现磁绳的加热很可能源于磁场重联。二、作为日冕物质抛射传播背景的太阳风的特性的研究：找到了冕羽作为太阳风重要源头的直接观测证据；发现宁静区可能是近地太阳风重要源头。三、作为日冕物质抛射能量孕育体的黑子及日珥的物理特性的研究：对黑子亮桥的几何特性有了新认识；发现了黑子上方大气中一类新活动现象。四、影响爆发事件热力学及动力学性质的核心机制--磁场重联—的研究：统计分析了日冕亮点的磁通供应；发现重联可能在过渡区冷环的加热中有着重要贡献。五、爆发释能区的物理参数的间接诊断：提出了诊断爆发释能区物理参数的若干新方案，研究了磁场强度推断值的不确定性。六、爆发事件作为脉冲式扰动源的后续观测效应的研究：为局域及大尺度日冕结构对日冕物质抛射的若干响应提供了物理理解。..共发表第一及通讯作者论文14篇（7篇ApJ、2篇A&A、3篇SoPh、2篇Phys Plasmas），此外发表合作论文若干。有关成果曾入选Hinode/EIS仪器组科研亮点，受到多次引用，施引文献包括发表于Living Reviews in Solar Physics和Solar Physics上的综述。..在项目资助下，项目承担人受邀成为国际空间研究所(ISSI)择优资助的“低速太阳风起源”国际组成员，并合作完成综述论文一篇，发表于领域重要综述期刊Space Science Reviews；承担人受邀成为国际空间科学研究所（北京，ISSI-BJ）择优资助的“日冕磁震学”国际组成员。在亚洲大洋洲地球科学学会(AOGS)2012至2017年会上召集了“太阳风湍流”分会场，在国际地磁与高空物理协会(IAGA)2015科学大会上组织了“太阳大气及太阳风中的波动与湍流”专题会议。共收到来自IAGA科学大会、国际等离子体物理大会(ICPP)、国际空间等离子体流动会议(AstroNum)等国际会议9次邀请报告约请。承担人作为Guest Editor，在JGR上组编了太阳风湍流相关的专栏(Special Section)。在项目资助期内，承担人还受到山东省自然科学杰出青年基金支持。