Collisional and viscous damping of MHD waves in partially ionized plasmas of the solar atmosphere

¹ Space Research Institute, Austrian Academy of Sciences, Schmiedlstraße 6, 8042 Graz, Austria e-mail: maxim.khodachenko;helmut.rucker@oeaw.ac.at

² Physics Department, University of Warwick, Coventry, CV4 7AL, UK e-mail: t.d.arber@warwick.ac.uk
³ Institute for Geophysics, Astrophysics and Meteorology, Universtitätsplatz 5, 8010 Graz, Austria e-mail: arnold.hanslmeier@uni-graz.at

Received: 18 August 2003
Accepted: 6 April 2004

Abstract

Magnetohydrodynamic (MHD) waves are widely considered as a possible source of heating for various parts of the outer solar atmosphere. Among the main energy dissipation mechanisms which convert the energy of damped MHD waves into thermal energy are collisional dissipation (resistivity) and viscosity. The presence of neutral atoms in the partially ionized plasmas of the solar photosphere, chromosphere and prominences enhances the efficiency of both these energy dissipation mechanisms.
A comparative study of the efficiency of MHD wave damping in solar plasmas due to collisional and viscous energy dissipation mechanisms is presented here. The damping rates are taken from Braginskii [CITE] and applied to the VAL C model of the quiet Sun (Vernazza et al. [CITE]). These estimations show which of the mechanisms are dominant in which regions. In general the correct description of MHD wave damping requires the consideration of all energy dissipation mechanisms via the inclusion of the appropriate terms in the generalized Ohm's law, the momentum, energy and induction equations. Specific forms of the generalized Ohm's Law and induction equation are presented that are suitable for regions of the solar atmosphere which are partially ionised.