  To elucidate the flare trigger mechanism, we have analyzed several flare
events which were observed by Hinode/Solar Optical Telescope (SOT), in our
previous study. Because of the limitation of SOT field of view, however, only
four events in the Hinode data sets have been utilizable. Therefore, increasing
the number of events is required for evaluating the flare trigger models. We
investigated the applicability of data obtained by the Solar Dynamics
Observatory (SDO) to increase the data sample for a statistical analysis of the
flare trigger process. SDO regularly observes the full disk of the sun and all
flares although its spatial resolution is lower than that of Hinode. We
investigated the M6.6 flare which occurred on 13 February 2011 and compared the
analyzed data of SDO with the results of our previous study using Hinode/SOT
data. Filter and vector magnetograms obtained by the Helioseismic and Magnetic
Imager (HMI) and filtergrams from the Atmospheric Imaging Assembly (AIA) 1600A
were employed. From the comparison of small-scale magnetic configurations and
chromospheric emission prior to the flare onset, we confirmed that the trigger
region is detectable with the SDO data. We also measured the magnetic shear
angles of the active region and the azimuth and strength of the flare-trigger
field. The results were consistent with our previous study. We concluded that
statistical studies of the flare trigger process are feasible with SDO as well
as Hinode data. We also investigated the temporal evolution of the magnetic
field before the flare onset with SDO.
