ANOTHER CLUE ABOUT PARTICLE-ACCELERATION IN IMPULSIVE HARD X-RAY MICROWAVE BURSTS/

In a sample of impulsive bursts with rise times less than 30 s, a corr elation between burst rise times and the frequency of maximum microwav e emission has been found. The implications for source structure and d ynamics are discussed in this paper. Previously evidence was found tha t such bursts are caused by some propagating disturbance such as a sho ck wave or thermal conduction front. Combining that evidence with the microwave and hard X-ray spectral information suggests that the most r apid bursts are emitted from the most compact and intensely magnetized sources. The most rapid bursts also exhibited the hardest X-ray spect ra, as published previously. These facts are important clues to unders tanding the physical process responsible for impulsive bursts. A model for the bursts is suggested, based on the observations and inferences described.