Dissipating the energy of magnetoacoustic waves in a structured atmosphere

The distances over which magnetohydrodynamic waves will propagate in a non-ideal, magnetic, compressible medium, representing the solar corona structured by the presence of loops of denser material, are considered. The waves are damped by ion viscosity and electron heat conduction in a radiating, optically thin atmosphere. Waves which lose their energy of propagation in distances of less than our criterion value of 4 × 10⁹ cm are regarded as candidates for contributing towards coronal heating. Alfvénic-type waves only dissipate in this way in weak ( 15 G) magnetic fields and when they have periods of a few seconds (210 s). Acoustic-type waves can also be dissipated and we give typical values of magnetic field strength, density and temperature for which the dissipation could occur. Dissipating acoustic-type waves have periods that range from tens to hundreds of seconds (15–225 s).Calculations show that reliable measurements of velocity amplitudes will be invaluable in deciding whether these dissipating waves can contribute to heating the corona. We suggest that the waves that survive dissipation may account for some of the observed coronal oscillations.