A study of the magnetic and velocity fields in an active region

A time sequence of magnetograms and velocity-grams in the Hα and Fe I 6569 A lines has been made at a rate of 12 h-1 of McMath Region 10385 from 26 to 29 October, 1969. The 14 flares observed during this period have been studied in relation to the configuration and changes in the magnetic and velocity fields. There was little correlation between flare position and the evolutionary changes in the photospheric magnetic and velocity field, except at large central meridian distances where the velocity observations suggested shearing taking place at flare locations. At central meridian distances > 300 it was found that flares are located in areas of low line-of-sight photospheric velocity surrounded by higher velocity hills. The one exception to this was the only flare which produced a surge. Blue-shifted velocity changes in the photosphere of 0.3 to 1 kms1 were observed in localized areas at the times of 8 of 14 flares studied. (Auth.)