The Association of Solar Optical Flares with Type III Solar Bursts from 4 TO 2 MHz Observed by Ogo-III

Type III solar radio bursts from 4 to 2 MHz observed by OCO-IlI have been associated with optical flares and, hence, with solar plage regions. A radio burst was considered to be flare associated if it occurred within 10 min of the reported flare maximum. With this criterion, 70 percent of the radio bursts were found to be associated with flares or subflares. On the average, the burst preceded the reported flare maximum by 1.45 min. The plage regions associated with the greatest number of radio bursts were, in general, those which were largest, brightest, and of greatest sunspot area and field strength. Since radio bursts are thought to originate in coronal streamers, it is inferred that these plage regions are associated with coronal streamers of radial length SR0 or greater. The data suggest that a major change in filament or sunspot structure in a large plage region can temporarily create or enhance the conditions necessary for the propagation of electron streams to large radial distances and that well-established streamers maintain their integrity and magnetic-field structure for as long as two solar rotations.