Sunspot Motions Associated with Flares

Abstract

The evolution of five bipolar sunspot groups during their disk passage leading to flares are analysed and studied using Kodaikanal Observatory photoheliogram and spectroheliogram data. The changes in the orientation angle observed in the spot groups show that sunspot proper motion plays an important role in introducing nonpotential character to the field lines. This in turn develops shear and once the shear reaches a critical value, the flare eruption is triggered. The rotational motions in the sunspots are measured from the change in their orientation angle and are given as a measure of shear. The sunspots considered for analyses in the present study are not associated with any filament activity.