Observations of Temporal Fine Structures in Solar Millimeterwave Bursts

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The objective of this research is to estimate observationally the time scale of particle acceleration in solar flares. We observed 21 events with the 35-GHz Polarimeter for solar activity monitor during from 1990 through 1992. These events were chosen under the criterion that flux density at 35GHz was greater than 2500 sfu.Main results of analyses of the data are as follows.1. Peak-to-peak time intervals in time profiles ranges from 0.5 to 500 s. Only 7 % shows peak-to-peak time intervals less than 1 s.2. Average peak-to peak time interval for each event is proportional to the rise time or the decay time of the event.3. The above observational results suggest that the time scale of particle acceleration in large solar flares ranges from 1 s to 100 s fot most events, and that the most rapid time scale is about 0.5 s.