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.
