Authors: Eirik Endeve, Egil Leer; Thomas E. Holzer
Affiliation: Institute of Theoretical Astrophysics, University of Oslo; National
Center for Atmospheric Research, High Altitude Observatory
We present results from a recent study of an axis-symmetric, two-fluid, magneto-hydrodynamic (MHD) model of an electron-proton solar corona with a dipole magnetic field (Endeve et al. To appear in ApJ, March 2004). Two-fluid effects (separate electron and proton energetics, and collisional coupling between the particle species) are included in the model, and we allow for electron and proton heating. Field-aligned thermal conduction is included in the energy equations. Heating of the coronal gas results in a magnetic field configuration with a helmet streamer, surrounded by coronal holes. The collisional coupling between electrons and protons is weak. In the case of proton heating the streamer proton temperature must be high (~ 4 MK) in order for protons to balance the applied heating by thermal conduction. In the coronal holes, where the solar wind is accelerated, the proton temperature is lower. (The electron temperature is significantly lower than that of protons.) A large pressure jump across the streamer-coronal hole boundary results in an unsteady streamer structure. When the equations are integrated on long timescales (on the order of 100 hours) streamer plasma is periodically released into the solar wind. The streamer material contributes significantly to the mass and energy flux in the solar wind.