Filamentation of magnetic structures and particle acceleration in solar and stellar flares

Abstract

We review models for the evolution and energy release of active region magnetic fields. We propose that turbulent photospheric motions will break the active region magnetic field in small fibers (current carrying magnetic filaments) and we address the possibility that this type of magnetic topology may become the host of thousands of neutral sheets. We have subsequently analyzed the acceleration and transport of energetic particles in such an environment. Standard techniques such as stochastic or shock acceleration, E-field acceleration or coherent acceleration are reviewed on the basis of a “statistical flare” model, where many explosions are organised (self-organised when they reach a critical stage or externally driven by emerging flux or large scale photospheric flows around filaments) to create a flare (micro-flare or large flare).