Surface Alfven Wave Contribution to Coronal Heating in a Wave-Driven Solar Wind Model
Abstract
We present results from the development of a solar wind model driven by a spectrum of Alfven waves with realistic damping mechanisms in the Space Weather Modeling Framework. Whereas other works have focused on the dissipation of wave energy in closed magnetic field regions or along open polar field lines, we emphasize here the boundary between these two regions as a source for coronal heating and wind acceleration. This region is characterized by gradients in density and magnetic field, that set up a resonant layer in which surface Alfven waves arise and dissipate their energy to the solar wind. Observations of latitudinal density distributions at 1.035-1.225 solar radii from differential emission measure tomography (Vasquez, Frazin & Manchester 2009) show density enhancements at the boundary of open and closed magnetic fields, which supports the presence of surface Alfven wave damping in this region. We utilize a first principle solar wind model within the Space Weather Modeling Framework. The wave transport equation, including wave advection and dissipation, is coupled to the magnetohydrodynamics equations for the plasma. We extend this model to include surface Alfven wave damping. We provide the first global damping length map for surface Alfven waves in a realistic background solar wind. We quantify the contribution of the damping to coronal heating and acceleration of the wind.
The boundary conditions for this solar wind model are obtained from observations and a semi-empirical model. The velocities at 1AU obtained from the semi-empirical Wang-Sheeley-Arge model in combination with conservation of the total energy density along the magnetic field lines determines the Alfven wave pressure at the lower coronal boundary. The electron density and temperature at the lower solar boundary are obtained from the differential emission measure tomography applied to the extreme ultraviolet images of the STEREO A and B spacecraft. This new solar wind model is validated with ACE data for Carrington rotation 2077 (2008, November 20 through December 17). Overall, the simulated results at 1AU match the ACE observations rather well.- Publication:
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Solar Heliospheric and INterplanetary Environment (SHINE 2010)
- Pub Date:
- July 2010
- Bibcode:
- 2010shin.confE.119E