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.

磁性螺旋度是一个物理变量，可以量化磁场通量的总链接数。由于磁性螺旋度是理想的磁流失动力学（MHD）过程中的保守量，并且是磁自由能的代理，因此人们普遍认为，磁性螺旋性可以作为MHD活动的示踪剂和驱动力起作用。我们已经研究了太阳 - 地球连接系统中磁性螺旋的动力学。首先，我们开发了基于Madnetogram观测值测量跨太阳能表面的磁性螺旋通量的方法，并发现进入太阳电晕的螺旋性注射与太阳能电晕中的软X射线排放活性非常相关。其次，我们开发了一种新的数值工具，可以从矢量磁图中重建太阳能电晕中的三维磁场，并将其应用于新的太阳能卫星观测值hinode提供的数据。结果，我们揭示了弹片前阶段中的磁场确实具有剪切的结构，它与两型式的杂音相吻合，这是一致的，这是在两型式的镜头上，并且在彼此的范围内呈现出来。第三，我们为理想的MHD方程（称为HUD方案）创建了最新的数值方案，并证明HLLD方案的计算性能优于任何以前的方案，以实现计算的准确性，稳健性，效率和易用性。最后，我们已将HLLD方案应用于太阳冠模拟，该模拟完全包括球形几何形状以及磁层模拟，其中考虑了更多的通用状态方程。太阳冠状模拟表明，驱动冠状质量弹出（CME）发作的临界磁性螺旋性对磁螺旋注射的空间结构敏感。