Spectral line width decrease in the solar corona: resonant energy conversion from Alfv{é}n to acoustic waves

Observations reveal an increase with height of the line width of several coronal spectral lines probably caused by outwardly propagating Alfv{é}n waves. However, the spectral line width sometimes shows a sudden decrease at a height 0.1-0.2 R, where the ratio of sound to Alfven speeds may approach un... View More