Solar flares observed with GOES and AIA

We explore the spatio-temporal evolution of solar flares by fitting a radial expansion model r(t) that consists of an exponentially growing acceleration phase, followed by a deceleration phase that is parameterized by the generalized diffusion function r(t){prop.to}{kappa}(t-t_1_)^{beta}/2^, which includes the logistic growth limit ({beta}=0), sub-diffusion ({beta}=0-1), classical diffusion ({beta}=1), super-diffusion ({beta}=1-2), and the linear expansion limit ({beta}=2).

We analyze all M- and X-class flares observed with Geostationary Operational Environmental Satellite and Atmospheric Imaging Assembly/Solar Dynamics Observatory (SDO) during the first two years of the SDO mission, amounting to 155 events. We find that most flares operate in the sub-diffusive regime ({beta}=0.53+/-0.27), which we interpret in terms of anisotropic chain reactions of intermittent magnetic reconnection episodes in a low plasma-{beta} corona.