A Study of Connections between Solar Flares and Subsurface Flow Fields of Active Regions

Gao Yu gy@bao.ac.cn, Key Laboratory of Solar Activiry, National Astronomical Observatories, Chinese Academy of Sciences
Zhao Junwei, W.W. Hansen Experimental Physics Labratory
Zhang Hongqi, Key Laboratory of Solar Activiry, National Astronomical Observatories, Chinese Academy of Sciences

Abstract
We investigate connections between solar flares and subsurface flows of the active regions. The flare parameter used in this study is the X-ray peak flux observed by the Geostationary Operational Environmental Satellites (GOES), and the subsurface flows are obtained from time-distance data-analysis pipeline for Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). The high temporal resolution of the observation allows us to study the hour-level evolution of the physical parameters of subsurface flows as well as their relations with solar flares. A few active regions having flare(s) above M-class are analyzed. It is found that the kinetic helicity , with a weight of speed, often show bumps near the flare peaks of the X-ray flux, implying there are some connections between subsurface kinetic helicity and solar flares. Additionally, the amplitudes of the velocity multiplying magnetic field in the active region rapidly varies with the time, especially around the peak time of the X-ray flux for some cases. These results imply that the kinetic helicity may be a good indicator for solar flares in subsurface flows and worth monitoring closely with more events. The relationship between the subsurface flow field, kinetic helicity, magnetic field, and solar flares is rather complicated and needs more detailed investigations.