Measurement of Magnetic Helicity Injection and Free Energy Loading into the Solar Corona

Abstract

We develop a new methodology that can determine magnetic helicity flux as well as Poynting flux across the photosphere based on magnetograph observation. By applying this method, we study the injection mechanism of magnetic helicity and magnetic free energy into the solar corona. In order to derive the helicity and energy fluxes, first the velocity tangential to the solar surface is constructed by applying a correlation tracking technique on the magnetic observation, and second, the velocity component normal to the photosphere is derived from the condition that the magnetic evolution must be consistent with the induction equation. Through this procedure, we can determine the helicity and energy fluxes separately for the shear motion effect and for the flux emergence effect. Based on this new method, NOAA Active Region 8100 was analyzed from 1997 November 1 to 5 using data observed by the Solar and Heliospheric Observatory Michelson Doppler Interferometer and the vector magnetograph at the National Astronomical Observatory of Japan (NAOJ) in Tokyo. The results indicate that the photospheric shear motion and the flux emergence process have equally contributed to the helicity injection and have supplied magnetic helicity of opposite signs into this active region.