Helioseismic analysis of active regions using HMI and AIA data



We apply the ring-diagram technique to analyze three active regions located near the central meridian. Using Doppler, continuum intensity, and line depth images from the Helioseismic Magnetic Imager (HMI), we investigate the variation in the high-degree mode asymmetry, frequencies, and horizontal flows. We find that the sub-surface zonal and meridional flows do not change significantly with the choice of different observables representing different heights in the solar photosphere, while the mode frequencies differ. We also examine the 2-d acoustic power distribution using data from HMI and the Atmospheric Imaging Assembly (AIA) 1600 and 1700 Å bands (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)