太阳物理研究组知识库

作为汪景琇院士主持的中国科学院数理学部“天体辐射磁流体力学”战略研究项目组成部分[1]，从等离子体的动力学属性出发，介绍了用于研究等离子体与周围磁场结构相互作用的粒子云网格方法，及其在研究具有复杂等离子体和磁场结构的磁重联过程中的应用。这里提到的磁场与等离子体的复杂性包括变化的等离子体 值，磁重联电流片中包含有多种尺度的结构，以及这些结构之间的相互作用，而且这些结构的尺度变化范围很大(从105km变化到102km)。进一步探讨了该方法在太阳物理领域，特别是在太阳爆发磁重联过程方面的可能应用以及未来的发展；并为项目研究中其他部分在数值方法[2{5]和太阳物理[6,7]方面提供借鉴和补充。

The particle-in-cell (PIC) method, employed since the 1940s, has become one of the preferred tools since 1980s in Magnetohydrodynamics numerical simulation field. In this work, the history, fundamentals, recent advances and future challenges of PIC are introduced from the statistical mechanics and solar fractal turbulent magnetic reconnection aspect. The fractal turbulent current sheet (FTCS) structure as a source for both small-scale reconnections,leading to nano-flares and to larges-scales one, leading to long-duration flares or giant arcades. It becomes now very attractive in solar flare and flare-like (e.g. CME) phenomena research as it can address many open issues in coronal heating and particle acceleration field.The large scale single FTCS involving multiple current sheets inevitably inherit the same sizeand time-step problems, allowing us to simulate macro turbulent and particle acceleration in only a very small region. PIC, a full kinetic approach, is suitable to exploring the turbulent dynamic mechanism and multiple turbulent fractal properties. But the narrowness of the simulation region still imposes strong limitations on the number of particles being accelerated in PIC simulations.