Examination of solar radio burst onsets in view of different flare scenarios and pre-flare structures

The time profiles of the solar microwave emission exhibit various phenomena reflecting the evolution of magnetic flux tubes before and during the onset of flare events. Different scenarios may be used to describe the processes of energy release in a flux tube and the interaction of a number of tubes during the pre-flare stage and the early flare development. Multi-peak structures at quite different time scales displayed by flux records at mm-, cm-, and dm-waves are examined; they raise the question of how to distinguish between repeated energy release on one site and the propagation of the flare disturbances over an extended source area. Observed time scales and released energy in the frame of some scenarios are discussed. (author). 3 figs., 17 refs