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

• Published in: Solar physics Vol. 47; no. 1; pp. 233 - 246
• Main Authors: Harvey, K. L., Harvey, J. W.
• Format: Journal Article
• Language: English
• Published: 01-03-1976
• ISSN: 0038-0938; 1573-093X
• DOI: 10.1007/BF00152261

A time sequence of magnetograms and velocitygrams in the H alpha and Fe I 6569-A lines was made at a rate of 12 hr super(-) super(1) of McMath Region 10385 from Oct. 26-29, 1969. The 14 flares observed during this period were 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 > 30 degrees . it was found that flares are located in areas of low line-of-sight photospheric velocity surrounded by higher velocity hills. The one exception was the only flare that produced a surge. Blue-shifted velocity changes in the photosphere of 0.3 to 1 km sec super(-) super(1) were observed in localized areas at the times of 8 of 14 flares studied.