Self-introduction Misawa

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Disaster Science Division
Space Environment Disaster Research
Hiroaki Misawa (Associate Professor)


Research summary


       We have investigated the disaster science relating to the sun, especially the study to realize a regular observation of solar radio bursts for monitoring critical conditions of solar activities.
       In the vicinity of the solar surface, explosive variations such as flares and CMEs (Coronal Mass Ejection) occasionally occur. In some cases, the solar variations are accompanied by generation of many energetic particles whose speed is more than 10% of the light speed, and such the event is called SEP (Solar Energetic Particle). If a SEP event happens at the most hazardous level, the radiological dosage to astronauts is estimated to be 1Sv at the orbital altitude of space stations. Such the SEP event causes serious radiation damages to the astronauts and also to electric devices installed in artificial satellites and spacecraft. So the early warning against SEP events is one of important subjects in the space environment disaster researches.
       It is known that large scale SEP events are accompanied by some type of solar radio bursts named Type-II with the wide frequency range in many cases. Since a radio wave travels with a light speed, the Type-II bursts reach the earth in about 8 minutes. On the other hand, SEP reach the earth in more than 30 minutes for a few tens MeV protons. This traveling time difference between radio waves and SEP gives an advantage for early warning of occurrence of large scale SEP. We have investigated generation processes of SEP and solar radio bursts and their relations to realize early warning the solar hazardous conditions based on development of wide frequency range radio receiving systems which enable us to make regular observations of solar radio waves.