AAS 204th Meeting, June 2004
Session 31 Hale Prize Lecture: The High Energy Sun
Invited, Monday, May 31, 2004, 3:40-4:30pm, 603/605/607

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[31.01] The High Energy Sun

R.P. Lin (UC Berkeley)

The Sun is a prolific and efficient particle accelerator. Large solar flares, the most powerful explosions in the solar system, accelerate ions up to tens of GeV and electrons up to hundreds of MeV, well into the energy range of galactic cosmic rays. Collisionless shock waves driven by fast coronal mass ejections accelerate particles to comparably high energies. In large and small flares, the accelerated particles often contain the bulk of the energy released, indicating the acceleration is intimately linked to the flare energy release process, most likely magnetic reconnection. Interestingly, the average rate of flare energy release, integrating down to micro/nano-flares, may be important for heating of the corona. High in the corona, frequent small impulsive accelerations produce \neg 0.1-100 keV electrons that escape to the interplanetary medium. Often these events also accelerate ~ 10 keV to MeV per nucleon ions that are enriched in heavy elements and enormously enriched in the isotope 3He. In addition, a non-thermal > 1 - 100 keV electron population, the ``superhalo," is continuously present in the interplanetary medium, even at solar minimum, suggesting a steady-state coronal acceleration process. I will present recent results from the RHESSI (Ramaty High Energy Solar Spectroscopic Imager) spacecraft, including the first hard X-ray imaging spectroscopy, the first high resolution nuclear gamma-ray line spectroscopy, and the first gamma-ray line imaging of solar flares; together with energetic particle observations from interplanetary spacecraft; and discuss the implications for the particle acceleration and energy release processes.

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