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

Park, Sung-Hong, Guerra, Jordan A., Gallagher, Peter T., Georgoulis, Manolis K. and Bloomfield, Shaun (2018) Photospheric Shear Flows in Solar Active Regions and Their Relation to Flare Occurrence. Solar Physics, 293 (8). ISSN 0038-0938

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Park et al - Photospheric Shear Flows in Solar Active Regions and Their Relation to Flare Occurrence AAM.pdf - Accepted Version
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Official URL: http://dx.doi.org/10.1007/s11207-018-1336-z

Abstract

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 co-aligned pairs of AR vector magnetograms with 12-min separation over the period 2012-2016. From each AR flow-field map, three shear-flow parameters were derived corresponding to the mean (), maximum (S_max) and integral (S_sum) shear-flow speeds along strong-gradient, strong-field MPIL segments. We calculated flaring rates within 24 hr as a function of each shear-flow parameter, and also investigated the relation between the parameters and the waiting time ({\tau}) 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 {\tau} 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.

Item Type: Article
Uncontrolled Keywords: Active regions - magnetic fields, Active regions - velocity field, Flares - relation to magnetic field, Velocity fields - photosphere
Subjects: F300 Physics
F500 Astronomy
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: Paul Burns
Date Deposited: 12 Sep 2018 16:25
Last Modified: 11 Dec 2018 12:30
URI: http://nrl.northumbria.ac.uk/id/eprint/35679

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