行星际CME和CIR的磁流体动力学和遥感观测表现的对应关系

Coordinated remote-sensing imaging in white light and interplanetary scintillation (IPS) can routinely monitor a wide field of the inner heliosphere from multiple vantage perspectives. Interplanetary disturbances such as coronal mass ejections (CMEs) and corotating interaction regions (CIRs) are continuously tracked in optics and radio. However, remote sensing signals are as a result of line-of-sight integration of weighted electron density. The weighted factors are determined by relative geometry between the light source, scattering sites, and a receiver. Specifically, the relative geometry refers to a Thomson scattering sphere in white light and a Fresnel filtering radius in IPS. At large elongations from the Sun, inversion and interpretation of remote sensing signals suffer from large uncertainties. For instance, kinematics models and unverified assumptions are used in interpreting brightness patterns of CMEs and CIRs imaged by the STEREO/HIs, and reconstructing 3D distribution of electron density from IPS tomography. In this proposal, we plan to construct a numerical MHD model of interplanetary space, model CMEs and CIRs, uncover the dynamics of CME-CME interacting and CME-CIR coupling, calculate synthetic observations in optics and IPS, compare modeling results with realistic observation events, and improve the understanding of interplanetary large-scale dynamics and remote-sensing imaging capabilities.

白光和行星际闪烁(IPS)的遥感技术已实现内日球层的大视场、全天候、多视角的联合成像，具备对行星际扰动的深空遥测能力，能连续跟踪日冕物质抛射(CME)和共转流相互作用区(CIR)的传播和演化。但遥感信号接收到的是沿视线方向的积分效应，涉及电子密度的加权之和。该权重因子取决于光源、散射体、接收者之间的相对几何位置，具体是白光的Thomson 散射球和IPS的Fresnel滤波半径等。遥感信号的反演和推断存在着较大的不确定性。比如，需要运动学模型和先验假设，才能(1)解读日球成像仪所拍摄的CME和CIR的运动影像，(2)从地面射电望远镜的IPS层析成像中反演电子密度的三维分布。本项目对行星际MHD过程建模，模拟CME和CIR扰动，揭示扰动与背景太阳风之间和多个扰动之间的相互作用，正演白光和射电的观测表现，进而将模型计算与具体观测事件比较，加深理解行星际的大尺度动力学和遥感成像技术的探测能力。

在青年基金的资助下，本项目在行星际动力学的可遥测信号和卫星探测计划的科学论证这两方面取得重要的科研进展：(1) 聚焦行星际扰动的日地传播过程，基于磁流体力学MHD数值模拟来正演行星际激波的白光影像表观，从而在物理机理上阐释STEREO/HI仪器所拍摄日冕物质抛射CME的运动白光影像；(2) 基于行星际CME白光亮度的正演模拟，详实论证白光日球仪在揭示行星际动力学和预报空间灾害天气的方面具有不可缺少的关键科学意义，从而为未来空间卫星计划搭载白光日球仪提供“科学目标定义与载荷配置方案”的科学论证。此外，本项目还探讨行星际CME的低频射电成像，分析其法拉第旋转的射电偏振信号，从而为地基行星际闪烁观测提供科学指导。通过本项目的执行，项目负责人发表第一作者的SCI论文两篇，深化国内外同行合作，进入“国际与日共存ILWS”框架下内日球层卫星探测计划（Solar Orbiter、Solar Probe Plus、SPORT、InterHelioProbe）的协调工作组。