Damping and Dispersion of Acoustic Waves in the Solar Corona

Abstract We study one of the most common phenomena in the solar corona—compression waves observed in the extreme ultraviolet range. They are observed throughout various coronal structures, coronal loops and holes. The widespread occurrence of compression waves makes them one of the best possible tools in coronal seismology for determining coronal plasma parameters. Over four decades of observations, a large number of papers have been devoted to them, and many of their properties are now well understood. The prevailing view in theoretical studies is that compression waves are acoustic or are magnetoacoustic waves generated in the lower layers of the atmosphere and propagating upward into the corona. Using an analytical representation of the coronal plasma radiative-loss function, we produce a detailed study of acoustic waves in the corona, whose behavior is mostly influenced by thermal conduction. A minimum appears in the period distribution of the group speed, closely linking the damping and dispersion of acoustic waves. The waves can be divided into two types, with short and long periods, which have fundamentally different properties. This circumstance allows us to develop a new concept of compression waves.