Alfvén waves in the structured solar corona
Abstract
A simple model of a periodic ensemble of closely packed flux tubes sitting atop a vertically stratified layer reveals that an incident fast wave from below preferentially converts almost immediately to Alfv\'en waves in the flux tubes, with kink waves restricted to at most a very few Fourier modes. This suggests that observations of coronal kink modes in such structured systems may greatly underestimate the net wave energy flux being transported into and through the corona, much of which may reside in harder-to-observe Alfv\'en waves. The processes of mode conversion/resonant absorption and Alfv\'en phase mixing are implicated. It is suggested that the Sun's internal p-mode field -- the 5-minute oscillations -- may contribute substantially to the process by supplying incident fast waves in the chromosphere that scatter and mode-convert in the tube ensemble.