Paper detail

A Helioseismic Survey of Near-surface Flows Around Active Regions and their Association with Flares

We use helioseismic holography to study the association of shallow flows with solar flare activity in about 250 large sunspot groups observed between 2010 and 2014 with the Helioseismic and Magnetic Imager on the Solar Dynamics Observatory. Four basic flow parameters: horizontal speed, horizontal component of divergence, vertical component of vorticity, and a vertical kinetic helicity proxy, are mapped for each active region during its passage across the solar disk. Flow indices are derived representing the mean and standard deviation of these parameters over magnetic masks and compared with contemporary measures of flare X-ray flux. A correlation exists for several of the flow indices, especially those based on the speed and the standard deviation of all flow parameters. However, their correlation with X-ray flux is similar to that observed with the mean unsigned magnetic flux density over the same masks. The temporal variation of the flow indices are studied, and a superposed epoch analysis with respect to the occurrence to 70 M and X-class flares is made. While flows evolve with the passage of the active regions across the disk, no discernible precursors or other temporal changes specifically associated with flares are detected.