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R. Lionello, J. A. Linker, Z. Mikic (Science Applications International Corporation)
The structure of the solar corona is dominated by the magnetic field. The MHD polytropic model based on observed photospheric fields captures many features of the large-scale corona. However the simplified energy equation in those models fails to reproduce the temperature structure of the corona and the observed contrast in speed between the fast and slow solar wind. We present some recent results obtained with our MHD model utilizing a more careful treatment of the thermodynamics. Our model includes thermal conduction parallel to the magnetic field, radiation, coronal heating, and Alfvén wave pressure. Thermal conduction is collisionally dominated in the inner corona, where it is calculated with Spitzer's formula, and smoothly becomescollisionless in the outer corona. At the base of the corona we can either impose radiation balance or we can model the transition region directly. In our simulations we specify a magnetic flux distribution on the solar surface and integrate the time-dependent MHD equations to steady state. The resulting solutions can be tested against observed properties of the corona and of the solar wind.
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