Photospheric Shear Flows in Solar Active Regions and Their Relation to Flare Occurrence 

SungHong Park Submitted: 20180722 19:31
Solar active regions (ARs) that produce major flares typically exhibit strong plasma shear flows around photospheric magnetic polarity inversion lines (MPILs). It is therefore important to quantitatively measure such photospheric shear flows in ARs for a better understanding of their relation to flare occurrence. Photospheric flow fields were determined by applying the Differential Affine Velocity Estimator for Vector Magnetograms (DAVE4VM) method to a large data set of 2,548 coaligned pairs of AR vector magnetograms with 12min separation over the period 20122016. From each AR flowfield map, three shearflow parameters were derived corresponding to the mean (S_{mean}), maximum (S_{max}) and integral (S_{sum}) shearflow speeds along stronggradient, strongfield MPIL segments. We calculated flaring rates within 24 hr as a function of each shearflow parameter, and also investigated the relation between the parameters and the waiting time (τ) until the next major flare (class M1.0 or above) after the parameter observation. In general, it is found that the larger S_{sum} an AR has, the more likely it is for the AR to produce flares within 24 hr. It is also found that among ARs which produce major flares, if one has a larger value of S_{sum} then τ generally gets shorter. These results suggest that large ARs with widespread and/or strong shear flows along MPILs tend to not only be more flare productive, but also produce major flares within 24 hr or less.
Authors: S.H. Park, J. A. Guerra, P. T. Gallagher, M. K. Georgoulis, D. S. Bloomfield
Projects: None

Publication Status: Accepted for publication in Solar Physics
Last Modified: 20180723 10:01


