Absorption of magnetoacoustic waves in the solar atmosphere with random inhomogeneities of density and magnetic fields

Abstract

Effects of a collection of strong and random inhomogeneities of the magnetic fields, plasma density, and temperature in the solar atmosphere on the propagation of magnetoacoustic waves of arbitrary amplitudes are numerically studied by using a one dimensional code of ideal magnetohydrodynamics. It is shown that even in the presence of strong, small scale background inhomogeneities long wavelength perturbations (λ ≫ R, where R is the scalelength of the inhomogeneities) steepen and form shock waves. Furthermore, the presence of small scale background fluctuations results in a much stronger dissipation of long wavelength perturbations and a larger heating of the plasma compared to the case of a homogneous medium. The limiting case of λ → R in which the wavelength of the perturbation is of the same order as the length scale of the inhomogeneities (this case is beyond the realm of the theoretical analysis of Ryutova et al. (1990)), dissipates its energy even faster and in fact so fast that the waves do not steepen into shocks. Compared to the case of long wavelength perturbations the heating of the plasma is even larger. We discuss the relevance to sunspots and magnetized regions of the solar atmosphere.