Heating of the solar and stellar coronae

Abstract

The problem of heating of the solar and stellar coronae by acoustic, magnetoacoustic and Alfven waves and by magnetic energy dissipation has been reviewed. Some miscellaneous mechanisms such as mass accretion, magnetic flux emergence, spicules and velocity filtration etc are also briefly described. Our analysis favours Alfven waves, magnetic energy dissipation and velocity filtration heating. In case of Alfven waves the generation and dissipation needs more precise study. For magnetic energy dissipation the instruments which can resolve length-scales of the order of 1 km at the solar surface are crucially needed. In order to test the validity of the velocity filtration theory the computation of the intensities of UV lines by taking into account Coulomb effects, realistic geometry and ambipolar diffusion must be available. Further the mechanism of production of high energy particles at the base of the corona is also highly desirable.