Study of Magnetic Helicity Dynamics in Solar and Space Plasmas

太阳和空间等离子体中的磁螺旋动力学研究

基本信息

批准号：
16540216
负责人：
KUSANO Kanya
金额：
$ 2.18万
依托单位：
Independent Administrative Institution, Japan Agency for Marine-Earth Science and Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

项目摘要

Magnetic helicity is a physical variable, which can quantify the total linking number of magnetic field flux. Since magnetic helicity is a conserved quantity in the ideal magnetohydrodynamic (MHD) process, and is a proxy of magnetic free energy, it is widely believed that magnetic helicity may play a role as tracer and driver of MHD activities. We have investigated the dynamics of magnetic helicity in the Sun-Earth connection system. First, we have developed the methodology to measure magnetic helicity flux across the solar surface based on the madnetogram observation, and found that the helicity injection into the solar corona is well correlated with the soft X-ray emission activity in the solar corona. Second, we have developed the new numerical tool to reconstruct the three-dimensional magnetic field in the solar corona from vector magnetogram, and applied it to the data provided by the new solar satellite observatory HINODE.. As a result, we have revealed that magnetic field in pre-flare phase indeed has a sheared structure, which is well consistent with the paring of two-ribbon appearing after the onset of flare. Third, we created the state-of-the-art numerical scheme for ideal MHD equation, called HUD scheme, and have demonstrated that the computational performance of HLLD scheme is better than any previous schemes for the accuracy, robustness, efficiency and handiness of computation. Finally, we have applied the HLLD scheme to the solar coronal simulation, which fully includes the spherical geometry, as well as to the magnetospheric simulation, in which more generic equation of state is taken into account. The solar coronal simulation has revealed that the critical magnetic helicity to drive the onset of coronal mass ejection (CME) is sensitive to the spatial structure of magnetic helicity injection.

磁螺旋度是一个物理变量，可以量化磁场通量的总链接数。由于磁螺旋度是理想磁流体动力学（MHD）过程中的守恒量，并且是磁自由能的代表，因此人们普遍认为磁螺旋度可能起到MHD活动示踪剂和驱动器的作用。我们研究了日地连接系统中磁螺旋度的动力学。首先，我们基于磁力图观测开发了测量穿过太阳表面的磁螺旋通量的方法，发现日冕的螺旋注入与日冕中的软X射线发射活动有很好的相关性。其次，我们开发了新的数值工具，可以从矢量磁图重建太阳日冕的三维磁场，并将其应用于新太阳卫星观测站 HINODE 提供的数据。耀斑前阶段的场确实具有剪切结构，这与耀斑开始后出现的两带配对非常一致。第三，我们创建了理想 MHD 方程的最先进的数值方案，称为 HUD 方案，并证明 HLLD 方案的计算性能在计算的准确性、鲁棒性、效率和便捷性方面优于以前的任何方案。。最后，我们将 HLLD 方案应用于太阳日冕模拟，其中完全包括球面几何形状，以及磁层模拟，其中考虑了更通用的状态方程。日冕模拟表明，驱动日冕物质抛射（CME）开始的临界磁螺旋度对磁螺旋度注入的空间结构敏感。