Models of the open solar atmosphere |
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| Authors: | M A Wragg E R Priest |
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| Institution: | 1. The University, St. Andrews, Scotland
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| Abstract: | McWhirter et al. (1975) have presented a standard model for the transition region and inner corona that matches with the Harvard Smithsonian Reference Atmosphere. They assume an open field line configuration and solve numerically the equations of energy and hydrostatic equilibrum. The purpose of the present paper is to generalise their model for the temperature and density as functions of height in several ways and, in particular, to determine the temperature maxium and its location. The effect of varying the following characteristics of the model is determined: - Boundary conditions on temperature and density;
- magnitude of the heating;
- form of the heating term;
- divergence of the field lines;
- presence of subsonic flows, either upward or downward.
If the heating is localised at great altitudes, it tends to produce a narrower and larger temperature maximum at a greater altitude than a uniform heating and even more so than a heating proportional to density. For fixed base conditions, an increase in heating or field line divergence or downflow decreases the coronal temperature and reduces the height of the temperature maximum, while a steady upflow has the opposite effects. A maximum possible upflow was found, beyond which a catastrophe occurs so that no steady hot solution exists. |
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