Measurement of magnetic helicity flux into the solar corona

We developed a new methodology which can determine magnetic helicity flux across the photosphere based on the magnetograph observation, In order to derive the helicity flux, first the velocity tangential to the solar surface is constructed by applying a correlation tracking technique on the magnetic observation, and secondly the velocity component across 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 flow across the photosphere as a function of time and space, Based on this new method, we analyzed magnetic helicity of the active regions NOAA 9026 and 9077. using the data taken by SOHO/MDI and the vector magnetograph at NAOJ/Tokyo. As a result, it was revealed that positive and negative helicity is supplied in each region simultaneously. In particular, temporary activation of the helicity injection of the both signs was observed prior to X-class flare events in the GOES classification. The investigation on the helicity distribution suggests some relationship between flare onset and the increase of complexity in the helicity structure.