Observations of Temporal Fine Structures in Solar Millimeterwave Bursts

1992 Fiscal Year Final Research Report Summary

• Project/Area Number: 02640208
• Research Category: Grant-in-Aid for General Scientific Research (C)
• Allocation Type: Single-year Grants
• Research Field: Astronomy
• Research Institution: National Astronomical Observatory
• Principal Investigator: NAKAJIMA Hiroshi NAO Division of Radio Astronomy, 電波天文学研究系, 助教授 (40012877)
• Co-Investigator(Kenkyū-buntansha): KAWASHIMA Susumu NAO Solar Radio Observatory, 野辺山太陽電波観測所, 助手 (40234059) ; SEKIGUCHI Hideaki NAO Solar Radio Observatory, 野辺山太陽電波観測所, 助手 (40154645) ; SAWA Masaki NAO Division of Radio Astronomy, 電波天文学研究系, 助手 (10154139) ; SHIOMI Yasuhiko NAO Division of Radio Astronomy, 電波天文学研究系, 助手 (00134627) ; SHIBASAKI Kiyoto NAO Division of Radio Astronomy, 電波天文学研究系, 助教授 (90023689)
• Project Period (FY): 1990 – 1992
• Keywords: Solar Millimeterwave Burst / Temporal Fine Structure / Solar Flare / Particle Acceleration

Research Abstract

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.