Abstract

Alfvén waves are shown to be readily generated by mode conversion from fast MHD waves reflecting of the steep atmospheric Alfvén speed gradient in active region atmospheres. A simple analytic description of this process in terms of an ‘interaction integral’ indicates that it is spread over many vertical scale heights, and indeed fills the whole active region chromosphere for waves of moderate helioseismic degree l even up to l = 1000 or more. This suggests that active region chromospheres are Alfvén wave factories.