Numerical simulations of two-fluid magnetoacoustic waves in the solar atmosphere

Abstract

ABSTRACT We study vertical variations of wave periods of magnetoacoustic two-fluid waves in the partially ionized lower solar atmosphere, consisting of ion (proton) + electron and neutral (atomic hydrogen) fluids, which are coupled by ion–neutral collisions. The study allows finding the wave period cut-offs and their variations in the solar atmosphere, as well as establishing the role of these cut-offs in determining the wave propagation conditions. The atmosphere is permitted by a uniform vertical magnetic field. We perform numerical simulations in the framework of a one-dimensional (1D), two-fluid model in which plane waves are exited by a harmonic driver in the vertical ion and neutral velocities, operating at the bottom of the solar photosphere. We observe excitation of waves with cut-off wave periods in addition to waves set directly by the driver. We also see that some waves exited by that driver can reach the solar corona. Despite of its limitations such as the lack of non-adiabatic and non-ideal terms and a simple 1D structure, the developed two-fluid model of the solar atmosphere sheds a new light on the role of cut-offs in setting up the wave propagation conditions in the solar atmosphere and finding periods of waves that may carry their energy from the solar surface to the corona.