Coronal Scale-Height Enhancement by Magnetohydrodynamic Waves

Abstract

We discuss the possibility that the transmission of Alfvén waves from the photosphere into coronal loops can increase the density scale height in these loops. The mechanism involved is the ponderomotive force of transmitted waves, which opposes the force of gravity. We propose that this effect may account for cool coronal loops observed by the Solar and Heliospheric Observatory (SOHO). We also suggest that it may be an explanation of the emission measure enhancement found at the top of coronal X-ray loops observed by Yohkoh.