The Sun as a Stellar Laboratory: Unsolved Problems

Abstract

Abstract.A brief overview is given of some of the current outstanding problems in solar physics with greatest emphasis on high energy phenomena in the atmosphere. The importance of plasma kinetic effects, as well as MHD, in understanding the complex finely structured and dynamic solar atmospheric plasma is stressed. Key results from the RHESSI Mission on energetic flare particle acceleration, propagation, and flare energy budgets are presented as are recent findings concerning the solar and stellar flare Neupert effect and the possible role of energetic particles in micro-events in the 'non-flaring' sun. Finally, evidence showing that magnetic fields are also important in hot star phenomena is mentioned.