ABSTRACT
The stressing of the Sun’s magnetic field by plasma motions from the deep interior through the photosphere, its visible surface, transfers the energy generated by fusion from the core to the plasma and magnetic field of the solar corona. The emergence and evolution of solar active regions, localized regions of strong magnetic flux that wax and wane with the solar cycle, cause significant fluctuations of emissions across the electromagnetic spectrum; enhancements in UV radiation and X-rays are particularly relevant to space weather because of their profound impact on planetary ionospheres. The starting point for the mean-field models is the separation of the dynamics between the slowly varying, global scale of the differential rotation, for example, and the small-scale, rapidly varying and statistically stationary scales of the convective turbulence. There are two principal classes of models for the magnetic configuration of filament-channel fields before eruption: twisted flux ropes and sheared arcades.
