The heating of the solar corona is an unsolved problem of general importance to astrophysics. The two main theories propose as driving energy input waves from the lower layers and the release of energy by electric currents in the corona.
Electric currents release free energy of the magnetic field.
Powerful energy inputs are observed in solar flares that are generally interpreted as impulsive releases of magnetic energy. However the regular flares do not have enough energy to heat the coronaa. For this reason, energy input by a large number of microflares has been proposed. Such flares have not yet been observed. An observing program is carried out that aims to compare 'heating events' as seen in X-ray and EUV to emissions in other wavelenths with diagnostic properties.