Current status of the dissipative thermal model for solar hard X-ray bursts

The existing dissipative thermal models for hard X-ray bursts are briefly examined, and it is shown that the model with additional acceleration is the best candidate for explaining the whole hard X-ray burst. In both phases, but especially in the thermal phase, the plasma beta approaches unity, and two-dimensional modeling of the hydrodynamics is required. Following the accelerated electrons only, without taking into account the response of the bulk of the plasma, is inadequate. It is suggested that a useful approach might be a multifluid one using approximately 15 fluids with the possibility of transfer between fluids in one and two dimensions. It is concluded that, while the model is a promising one, many details remain to be worked out.