Fast-to-Alfvén Mode Conversion and Ambipolar Heating in Structured Media. I. Simplified Cold Plasma Model

Abstract

Linear fast magnetoacoustic waves are introduced into a cold stratified plasma model made up of a doubly periodic ensemble of straight diminished-Alfvén-speed tubes. Coupling between fast and Alfvén waves is produced by stratification and the tube structures, and scattering is strong for wavelengths comparable to the inter-tube separation. Ambipolar diffusion is found to be enhanced by the structuring and is potentially significant at high frequencies. The production of kink waves is discussed and modeled. It is found that the tube structure significantly alters the wave energy reaching the corona and the form that it takes, even for moderate fast-slow tube contrast, with Alfvén waves becoming prominent.