磁螺度以及在太阳物理上的应用

Magnetic Helicity and Its Implication in Solarphysics

磁螺度应用到天体物理尤其是太阳物理上,从而变为一个热门的领域.螺度用以描述磁场的复杂结构,例如磁场的扭曲、缠绕、连结、编辫,作为一个物理量,与能量不同,在完全理想的磁流体力学(MHD)中,它是一个守恒量.在磁重联过程中,螺度近似守恒,应用到太阳大气上,可以计算磁螺度的传输.最近的观测发现在太阳上螺度存在南北半球的不对称性,北半球主要为负螺度,南半球正螺度占优势;阐述了在太阳大气不同层次这种不对称性的表现形式,并介绍了对这种规律的有代表性的解释;介绍了国际国内螺度研究的最新进展,指出了有待于解决的一些关键问题.

Magnetic helicity is a physics concept about magnetic field topological property. Recently, it is used in astrophysics,especially in solar physics. Now it is a very hot domain. Helicity can describes the field topological structure. It also can express the magnetic field complex structure, for example, twist, link, braid. As a physics quantity, in perfect magnetic hydrodynamics, it is conserved. During magnetic reconnection, helicity is approximately conserved. By using this characteristic to solar atmosphere, magnetic helicity transport rate is calculated. Recently,magnetic helicity asymmetry was found in different hemisphere of the sun. In the north hemisphere,helicity is predominate by negtivity; but in the south, helicity is almost positive. Hemisphere rule in the different layers of solar atmosphere is depicted and the reasons of this rule are introduced. The newest development of helicity research all over the world and its implications in solar physics are introduced. The problems which should be resolved are pointed out.