Coronal Restructuring and Particle Acceleration During Relativistic Solar Proton Events
Abstract
The early temporal evolution of four relativistic proton events of the current solar cy- cle is compared with broadband radio observations of nonthermal electrons and with images of coronal plasma structures (EIT, LASCO on SoHO). The events are accom- panied by fast and extended CMEs and flares. The data contradict the widely cited idea that flares - i.e. small-scale energy release in magnetically stressed structures of the corona - are irrelevant to the production of energetic particles detected at 1 AU during large "gradual" particle events: We show that radio sources at dm-m- (Nançay Radio Heliograph) cover angular ranges comparable to the CMEs. Even in cases where the flaring active region is poorly connected, a radio source is found close to the nominal Earth-connected interplanetary field line. The electron acceleration revealed by these sources lasts longer than the soft X-ray event. The accelerated electrons may attain mildly relativistic energies. The acceleration process is probably related with the re- structuring of the corona in the aftermath of the CME, at heights between 0.1 and 1 solar radius above the photosphere, but clearly not with the front of the CME and its presumed shock wave.
Since the solar release of the relativistic protons is delayed with respect to the flare onset during these events, but occurs during the long lasting radio emission, we argue that the coronal sites of electron acceleration are plausible sources of the relativistic protons detected at 1 AU, too.- Publication:
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EGS General Assembly Conference Abstracts
- Pub Date:
- 2002
- Bibcode:
- 2002EGSGA..27.3049K