Observations and Models of Coronal Heating

Abstract

Energy release in the solar Corona is characterized by a sequence of space and time localized events, whose intensity follows power-law distributions. In quiet Sun regions, small energy events, possibly under the detection threshold, dominate, thus supporting the “nanoflare” scenario of coronal heating. Two complementar models of heating are discussed, in connection with the above observational features. The first model is based on Alfvénic wavepackets dissipation in 3D force-free magnetic fields; the presence of regions of chaoticity of magnetic lines allows for a fast wave dissipation, within a fraction of a solar radius. The second model describes a MHD turbulence in low-β plasma, in which magnetic energy is continuously furnished by slow photospheric motions. Energy release events corresponds dissipation of current sheets, often associated with magnetic reconnection. The resulting distribution of dissipated power follows a power law, similar to observations.