Solar Avalanches and Cellular Automata: coronal magnetic energy release via an MHD avalanche
Prof Alan Hood (University of St Andrews)
Thursday 26th January, 2017 14:00-15:00 Maths 515
Solar flares can be thought of as a sudden and rapid release of a large amount of magnetic energy. Frequently the initial energy release occurs at one location and rapidly spreads along the whole structure. This has been modelled as an avalanche, using cellular automata, based on simple sand-pile models. These models seem to produce characteristics that are similar to solar observations, with the magnetic field existing in a state of self-organised criticality. Any additional stresses to the magnetic field in this state will immediately result in a release of energy. With this approach, large avalanches can model solar flares and lots of small avalanches can model the constant release of magnetic energy needed to heat the solar corona. One issue with this approach is that the cellular automata are based on simple rules that are not derived from the governing equations of Magnetohydrodynamics.
For the first time, we demonstrate how an MHD avalanche can occur in a multi-threaded coronal loop. The implications for coronal heating are discussed.