NONTHERMAL VELOCITIES IN THE SOLAR TRANSITION ZONE AND CORONA

Nonthermal velocities are presented for spectral lines covering the te mperature range 10(4)-10(6) K, measured from high-spectral-resolution data for several solar features observed at the limb by the high resol ution telescope and spectrograph (HRTS), including a coronal hole, 'qu iescent regions' and several small-scale active regions. These results are compared with predictions based on acoustic waves and heating via Alfven waves. It is likely that more than one mechanism is operating simultaneously, in particular, resonant Alfven wave heating, which is very sensitive to background plasma motions.