[PEM12-P02] Statistical study of active-region microflares observed with Hinode/XRT
Keywords:solar flare, coronal heating, X-ray
In order to investigate the frequency distribution in the energy range below 1027 erg, we analyzed high-cadence (3-6 sec) and high-resolution (1.03 arcsec/pixel) soft X-ray images taken with the X-Ray Telescope (XRT) onboard Hinode. The same active region was observed with four different filters repeatedly and the total observing time is 45 – 90 minutes for one filter. More than 10,000 events in total were automatically detected in the light curves of 4 x 4-pixel-binned XRT images. The frequency distribution was represented by a power-law in the energy range of about 1025.5 - 1027.5 erg. The shape of the distribution is similar to S95. However, the power-law index is different. Our result is about 2.2-2.6, larger than 2 though that of S95 is smaller than 2. This is a new finding for active-region microflares. Next, we compared the total energy loss rate and the total energy input rate by microflares detected in this analysis. It was found that the total energy input rate is much smaller than the total energy loss rate. However, there is a possibility if this distribution with the same power-law index extends to the smaller energy range because the power-law index α is larger than 2 in our study. Actually if the same distribution extends of ~ 1022 erg, then such smaller events can have enough energy to explain the active-region coronal heating.