I want to begin with the observation, which I will try to make clear in the following, that a solar flare comprises an incredibly complex set of phenomena. This is not only true with respect to what is seen and measured in spectacular examples, but also when one considers the constituent parts of simple, even idealized, cases. A series of different physical effects lead, as one illustration, to radiations from the flare-instability site and its surroundings which span the range from meter waves to gamma rays (Svestka 1976, Sturrock 1979).To fit within the context of this discussion, I will concentrate on the high-temperature and quasi-thermal aspects of a flare, and on the basic physical mechanisms connected with the primary energization and dissipation processes. Thus, I will treat the reconnection of the magnetic field, the bulk acceleration of particles, the thermalization and the ultimate radiation of the energy. I will not treat the optical manifestations or, at the other extreme, the acceleration of very high energy particles.
Erratum to: Multiple coulomb scattering for very-high-energy particles