Magnetic Helicity Injection, Free Energy Loading, and Solar Flares

We have developed a new scheme which can evaluate the influxes of magnetic helicity and magnetic energy through the photosphere based on magnetograph observations. 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 magnetograms, and secondly the velocity component across the photosphere is derived from the induction equation. Through this procedure, we can determine the contributions to the helicity and energy fluxes coming from the shear motion and the flux emergence separately. The application of this method to actual magnetograph data of NOAA region 8100 in 1997 revealed that the contributions to the helicity injection from the shear motion and the flux emergence were similar in magnitude, but they tend to have opposite signs. Interestingly, a series of flares occurred after the helicity injection showed the change in its sign.