Mild waves observed(?) by SOHO↔MHD wave heating

Data from the SUMER instrument onboard SOHO is used in an attempt to identify the dominant heating mechanism responsible for solar coronal heating. Analysing observational data obtained by SOHO in June-July 1996 at different temperature regions of the solar atmosphere we try to retrieve signatures of Alfven and/or magneto-acoustic waves as a function of the center-to-limb variation in UV line profiles. Confrontation of observations to theoretical studies in linear MHD do not clearly confirm the existence of MHD waves, although the clear center-to-limb dependence of the line widths rule out magneto-acoustic waves as the dominant heating mechanism. Further refinement to the model line width is required. The data clearly shows a difference in the line widths at disk center compared to the limb for low temperature ions, with only a small difference at coronal temperatures.