Heating of the solar corona.
Abstract
The author reviews a number of models which are currently being considered for coronal heating, but he considers also heating of the chromosphere. There are basically two types of models, which are motivated by a variety of observations. 1. Models which invoke MHD waves generated by the convective motions are motivated by observations of the ubiquitous presence of Alfvén waves in the solar wind. The solar wind provides one example of wave heating. Waves have the advantage of being able to heat the chromosphere and photospheric magnetic flux tubes on their way to the corona. A problem with wave theories is that the waves tend to be reflected by the steep Alfvén speed gradient in the chromosphere and transition region. 2. Models which invoke the gradual buildup of coronal magnetic energy due to random walks of the photospheric flux tubes, and the subsequent release of that energy via current sheet formation and reconnection, are supported by observations indicating that localized impulsive heating and dynamic events occur in the transition region and corona. These models cannot explain the chromospheric heating or the coronal heating on open field lines. A third possibility, which has not been studied in detail, is that the chromospheric and coronal heating is associated with emergence and cancellation of magnetic flux.
- Publication:
-
Computer Physics Reports
- Pub Date:
- May 1990
- DOI:
- 10.1016/0167-7977(90)90011-T
- Bibcode:
- 1990CoPhR..12..205H
- Keywords:
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- Solar Corona: Heating;
- Solar Corona: Magnetohydrodynamics