行星际闪烁谱和白光辐射像观测约束的三维磁流体层析反演日冕物质抛射的数值模型

Coronal mass ejections (CMEs) originate from the large-scale solar eruption, propagate along the "solar - interplanetary - geomagnetic" causality chain, and is a driver of space weather in the inner heliosphere. As a three-dimensional (3D) nonlinear transporting channel between Sun and Earth, interplanetary space can be observed by in-situ measurements and white-light imaging by deep-space spacecraft, and interplanetary scintillation (IPS) observations by ground-based low-frequency radio telescopes. The coronal and interplanetary white light brightness originates from Thomson scattering of incident sunlight by free electrons. The random modulations of the amplitude and phase of radio signatures from the distant compact radio sources are caused by density irregularities of interplanetary turbulence. In-situ measurements of interplanetary plasma and field are limited by the spacecraft orbits, whereas the field-of-view of white-light instruments and IPS facility can almost cover the full sky map of the inner heliosphere. Our proposal aims to construct a 3D numerical MHD model, analyze the observation data of STEREO/HI white-light images and Nagoya-IPS spectrum, use both spectrum and image observation to constrained MHD model parameters, perform a MHD computerized tomography inversion of the background solar wind and CME disturbance in three spatial dimension and one temporal dimension, reveal interplanetary propagation mechanisms of CMEs, and provide the scientific foundation of observation data analyses and the model support of space weather prediction for the forthcoming dedicated IPS facility within the Chinese Meridian Project.

日冕物质抛射CME源自太阳的大尺度爆发活动，沿“太阳-行星际-地磁”因果链依次传输，是内日球层空间天气的驱动源。行星际空间作为衔接日地两端的三维非线性传播通道，其观测手段有卫星就位测量、天基白光成像、地基行星际闪烁IPS射电信号。日冕和行星际的白光亮度来源于自由电子对太阳直射光的汤姆逊散射，IPS强度和相位的随机变化起源于行星际湍流密度不规则体对致密射电源信号所辐射电波的调制。行星际就位测量受限于卫星轨道，白光和IPS的视场范围能几乎覆盖内日球层的广袤天区。本项目拟构建行星际三维磁流体MHD数值模型，分析STEREO/HI白光辐射像和Nagoya-IPS闪烁谱的观测数据，采用谱像观测结合来约束MHD模型参数，通过MHD层析反演背景太阳风和CME扰动的三维空间分布和一维时间演化，揭示CME的行星际传播规律，为未来我国IPS观测数据分析及其空间天气预报应用提供前瞻性的科学储备和模型支撑。

在面上基金的资助下，本项目积极开展磁流体数值建模、日地空间的观测数据综合分析、深空卫星探测计划论证的紧密耦合研究，取得重要的科研进展并达到预期目标，共计完成论文7篇（其中第一作者的论文3篇）。主要研究成果可归纳为内日球层的白光辐射成像和射电强度闪烁这两方面：（1）基于数据驱动的三维磁流体力学数值模式来正演背景太阳风和日冕物质抛射CME扰动的白光辐射表观，预测不同视角下的CME白光辐射影像，为Parker Solar Probe和Solar Orbiter卫星观测提供科学指导，支撑我国太阳极轨探测和太阳立体探测等卫星计划的科学目标论证；（2）基于太阳风湍流介质中的射电波传播理论，开展行星际闪烁IPS的功率谱拟合和互相关分析，提出太阳风湍流的空间相关尺度和射电波衍射的菲涅尔半径是控制IPS衍射花纹的关键物理参数，反演太阳风整体流速和湍流谱等物理参数，支撑我国“十三五”重大科技基础设施子午工程二期行星际闪烁IPS射电望远镜的原始数据定标及其高级数据产品加工。