Spot and filament rotation in a sigmoidal flare

Abstract

The role played by the rotation of the umbrae in a sunspot with respect to the H? filament in inducing magnetic shear for the sigmoidal brightening is reported in this paper. We carried out these studies by using photoheliogram and filtergram data. In the absence of vector magnetogram at Kodaikanal, an alternative method has been attempted to evaluate shear by carefully analyzing the photospheric and chromosphric environment of the solar active regions. It has been found that a large value of shear change observed in the active region is responsible for the triggering of a sigmoidal related flare.