Surface Alfven Wave Damping in a 3D Simulation of the Solar Wind
Abstract
Here we investigate the contribution of surface Alfven wave damping to the heating of the solar wind in minima conditions. These waves are present in regions of strong inhomogenities in density or magnetic field (e. g., the border between open and closed magnetic field lines). Using a 3D MHD model, we calculate the surface Alfven wave damping contribution between 1-4 Rs (solar radii), the region of interest for both acceleration and coronal heating. We consider waves with frequencies lower than those that are damped in the chromosphere and on the order of those dominating the heliosphere. This work is the first to study surface Alfven wave damping in a 3D environment without assuming a priori a geometry of field lines or magnetic and density profiles. We demonstrate that projection effects from the plane of the sky to 3D are significant in the calculation of field line expansion. We determine that waves with frequencies >2.8 - 10^;ˆ’4 Hz are damped between 1-4 Rs. In quiet sun regions, surface Alfven waves are damped at further distances compared to active regions, thus carrying additional wave energy into the corona. We compare the wave contribution to the heating by a variable polytropic index and find that it is the same order. As it has been argued that a variable gamma acts as turbulence, our results indicate that surface Alfven wave damping is comparable to turbulence in the lower corona. This damping mechanism should be included self consistently as an energy driver for the wind in global MHD models.
- Publication:
-
Solar Heliospheric and INterplanetary Environment (SHINE 2009
- Pub Date:
- August 2009
- Bibcode:
- 2009shin.confE.131E