Computing Electric Currents in Solar Active Regions with HMI Vector Magnetograms

Electric currents in the photosphere may be good indicators of future solar activity. We investigate the time evolution of electric current patterns in a few active regions observed by the Helioseismic and Magnetic Imager (HMI). The electric currents are calculated by taking the curl of the HMI vector magnetograms. Using data from HMI has two main benefits. Since HMI continuously surveys the full solar disk with good resolution, no targeting is necessary; we are able to determine the currents before the active region forms, as well as during its emergence, rise, and decay. Also, since HMI is a space telescope, it provides frequent and consistent observations with which the time evolution of the current can be followed.