Evidence for Wave Heating of the Quiet Corona

Abstract:

We have inferred the properties of waves in quiet Sun regions based on spectroscopic line widths. The non-thermal line broadening is proportional to the amplitude of Alfvenic waves. Using a Potential Field Source Surface (PFSS) magnetic field model, we trace the evolution of line widths along inferred magnetic field lines. In order to mitigate line of sight effects, we select regions that are isothermal and where the field lines remain oriented close to perpendicular to the line of sight. Our results indicate that the waves are damped starting at a height that is positively correlated with the overall length of the loop. That is, for longer loops, the damping occurs starting at a larger height. This suggests that heating of quiet Sun loops occurs over a region centered on the loop top and extends over a large fraction of the loop. We estimate that there is enough energy flux in waves injected at the base of quiet Sun regions to account for coronal heating in such structures.