Damping and Dispersion of Non-Adiabatic Acoustic Waves in a High-Temperature Plasma: A Radiative-Loss Function

Abstract

The behavior of acoustic waves in a rarefied high-temperature plasma is studied; as an example, the plasma of the solar corona is considered. Effects of thermal conductivity and a heating/radiative loss are taken into account; data on a temperature distribution of a radiation intensity obtained from the CHIANTI 10 code are used. The classical Spitzer expression for a full-ionized plasma is used for the thermal conductivity. Based on the found values of the radiation-loss function, the cubic spline method is used to construct an approximate analytical expression necessary for studying linear waves. A dispersion relation is obtained, and a frequency, a phase speed, and a damping coefficient are found. Dispersion and damping properties are considered for a temperature of about 106 K and a particle density of about 1015m−3, which are typical for the coronal plasma. In sum, superiority in the dispersion and damping of the thermal conduction is shown; the heating and radiation loss manifest themselves at large wavelengths. In accordance with general results by Field, a condition was found under which the acoustic oscillations become unstable. It is shown that at certain values of the temperature and density, the wave damping is dominated by the heating/radiative loss misbalance. Thus, the earlier results on mechanisms of damping of observed acoustic waves in the solar corona are refined here.