Solar Flare Theory and the Status of Flare understanding

A review is given of out current understanding of the magnetohydrodynamics of solar flares. The theory of reconnection in 2D is now well understood, but in 3D we are only starting to understand the complexity of magnetic topology and the different ways in which reconnection may occur. Small flares may be driven by footpoint motions in emerging or interacting flux regions or they may occur at quasi-separatrix layers in complex regions.

For large eruptive two-ribbon flares, there has recently been a major advance in our understanding: first of all, an MHD catastrophe is likely to be responsible for the basic eruption; and secondly, the eruption then drives reconnection in the stretched-out field lines to create a set of rising soft x-ray loops. This model is well supported by numerical experiments and detailed Yohkoh observations. Particle acceleration may occur by turbulent or direct electric fields at the reconnection site or in the different kinds of MHD shock wave that are associated with the flare process.