Helicity Injection into the Solar Corona
Abstract
The aims of this paper are to consider the relation between the MHD stability and the magnetic shear in solar corona, as well as to develop the methodology to measure the helicity injection from magnetogram observations. We first numerically analyzed the resistive MHD stability of the magnetic arcades which have a variety of magnetic shear distribution. As a result of that, it is found that, while the total magnetic helicity is conserved, the typical structure of the most unstable mode is changed from the down-stream type to the up-stream type as the magnetic shear is localized in the center of the arcade. It implies the possibility that the filament eruption could be triggered by the localization of the magnetic shear. Secondly, we developed the methodology to measure the magnetic helicity injection due to the horizontal motion based on the magnetogram observation. The helicity injection can be calculated by dH/dt = int vec Vcdot vecA Bn dS, where vec V, vec A, and Bn are the horizontal velocity, the vector potential, and the magnetic field normal on the solar surface. Using the correlation tracking method of the magnetic field, the velocity vec V is constructed. The helicity injection in the active region NOAA 8100 from 1997 Nov. 2 to 3 is analyzed using the magnetic data observed by SOHO/MDI. It indicates that the evolution of the helicity injection has a certain correlation with the X-ray activity of the solar corona.
- Publication:
-
Multi-Wavelength Observations of Coronal Structure and Dynamics
- Pub Date:
- January 2002
- Bibcode:
- 2002mwoc.conf..151K