Electronic edition ISSN 1574-0579

Heating of the solar corona by Alfvén waves: magnetohydrodynamic calculation of the height temperature profile of the transition region

T. M. Mishonov , Y. G. Maneva , M. V. Stoev , A. M. Varonov

Faculty of Physics, St. Clement of Ohrid University at Sofia, 5 J. Bourchier Blvd., BG-1164 Sofia, Bulgaria

Abstract
The mechanism of solar corona heating still remains unexplained, almost 80 years after the discovery of the million degree hot solar corona. Observations show that the temperature increases more than one order of magnitude in the transition region, at the boundary between the solar chromosphere and the solar corona. We give a detailed magnetohydrodynamic (MHD) calculation of the height dependence of temperature and solar wind velocity. The temperature and solar wind velocity profiles are calculated for static frequency dependent spectral density of incoming MHD waves, no time dependent computer simulations have been performed. In our calculation we take into account only the Alfvén wave (AW) polarization. Other modes (slow- and fast-magnetosonic waves) do not create cooling. A self-consistent calculation of the MHD wave propagation through a static background of fully ionized hydrogen plasma in a weak magnetic field is made. Heated by these MHD waves, the background plasma temperature increases leading to a strong plasma viscosity increase, which results in a more efficient MHD wave absorption. Within this calculation, the width of the transition region is also evaluated by a maximum value of the temperature logarithmic derivative. Comparison of the calculated temperature profile with the available observational data show qualitative agreement. In such a way, after more than 70 years we return to the original Alfvén idea [Alfvén, H. 1947, MNRAS, 107, 211] that the solar corona is heated by AW. Tables 1, Figs 7, Refs 78.