Magnetic energy and magnetic helicity budget in AR 8210: What are the sources of flaring activity

摘要

The active region 8210 (AR, 8210) observed on May 1, 1998 is the site of numerous flares. By studying a time series (from 17:00 UT to 21:40 UT) of reconstructed coronal magnetic configurations, we give a scenario of the eruptive phenomena in AR 8210 involving the rotation of the sunspot and the complex topology in a reconnection process. We also study the time evolution of the energy and of the helicity budget. We compute the free energy in the corona, the magnetic energy rate due to transverse photospheric motions We conclude that the photospheric motions are related to flaring activities and occur before the injections of energy into the corona. In terms of magnetic helicity, we are able to derived the relative magnetic helicity (relative to the potential field) and the helicity of the potential field configuration. The vacuum helicity (or helicity of the potential field) is constant during the time period and characterizes the complex topology. For this time period, the relative magnetic helicity does not show obvious changes related to the flaring activity.