Resonant conversion of standing acoustic oscillations into Alfv{\'e}n waves in the $\beta ~ 1$ region of the solar atmosphere

Abstract

We show that 5-minute acoustic oscillations may resonantly convert into Alfv{\'e}n waves in the $\beta{\sim}1$ region of the solar atmosphere. Considering the 5-minute oscillations as pumping standing acoustic waves oscillating along unperturbed vertical magnetic field, we find on solving the ideal MHD equations that amplitudes of Alfv{\'e}n waves with twice the period and wavelength of acoustic waves exponentially grow in time when the sound and Alfv{\'e}n speeds are equal, i.e. $c_s \approx v_A$. The region of the solar atmosphere where this equality takes place we call a {\it swing layer}. The amplified Alfv{\'e}n waves may easily pass through the chromosphere and transition region carrying the energy of p-modes into the corona.