Current sheets as the source of heating for solar active regions

Observational data and theoretical arguments suggest that the heating source for an active region is the quasi-steady dissipation of magnetic field in current sheets. Effects in the solar atmosphere which are due to the presence of current sheets are considered. The most important of them is the heating of the chromosphere by the strong ultraviolet radiation of the current sheet. This can give rise to the brightening of an active region in optical emission. The energy flux from the current sheet in different ranges of the ultraviolet spectrum and the depths (column densities) into the chromosphere where this energy is absorbed are estimated.