Filament activity in a quiet region flare

We have taken the case of a circular Hα filament observed on May 9,1979 erupting into a double-ribbon flare associated with a non-spot region. The plage motions are responsible for the filament reorientation and, here as a special case, wherein the filament attains a clear circular shape before the onset of a flare. We conclude that the change in the orientation of the Hα filament marks the instability giving rise to the flare.