On radiative dissipation of sinusoidal compressive waves in the chromosphere

A first-order theory is developed for the radiative dissipation of compressive waves in the chromosphere above T _min, where line radiation becomes dominant. The radiative relaxation time, which is the key to dissipation, is shown to depend on wave amplitude, falling greatly for amplitudes 2 km s^–1 or more. For a given amplitude, dissipation is greatest for high frequencies, 0.1 s^–1, periods 1 min. The observed short-period r.m.s. velocities ~2.4 km s^–1 at the D₁, level are adequate to provide dissipation balancing chromospheric emission losses.Predictions for the temperature-velocity phase difference and the phase velocity are compatible with observations.