Physical Processes in the Lower Chromosphere of the Sun

Abstract

A specificity of the boundary between the photosphere and the chromosphere of the Sun consists in considerable acceleration of plasma spicules above this boundary and appearance of wave motions (predominantly Alfven waves). Analytical solution to the equations of magnetic hydrodynamics is constructed in the vicinity of this boundary from the chromosphere side. Expressions describing the growth of velocity of plasma spicules and the Alfven waves in this vicinity are derived. It is demonstrated that the vertical motion of the Alfven waves and spicules is accompanied by horizontal motion of plasma in the presence of a vertical component of magnetic induction. The obtained expressions characterize the diversity of directions and complexity of motions in the lower chromosphere. They demonstrate that the horizontal component of magnetic induction considerably increases near the lower boundary of the chromosphere. The vertical velocity of spicules among which fast spicules II are dominant and the velocity of the Alfven waves substantially increase in a very thin layer of the lower chromosphere, by a factor of 1.8 and 1.5, respectively. Estimates of the horizontal motion of spicules and the vertical component of magnetic induction are obtained.