Modelling the coronal helium abundance with low helium heating rates
Abstract
It is often assumed that all heavy ions, including helium, must be much hotter than the protons in order to escape the solar gravitational field and avoid large increases in abundance in the corona. However, in a recent study of iron in the slow solar wind, we have found that "cold" (i.e. with a temperature equal to the proton temperature) iron ions may in some cases escape from the corona simply through friction with the outflowing protons. In this study we will use a self-consistent gyrotropic model of the solar wind that stretches from the chromosphere to 1 AU and in which the only free parameters are the flow geometry and the particle heating parameters. An earlier study that was carried out using this model has shown that the coronal abundance of helium can be strongly enhanced if the helium ions do not receive a sufficient amount of energy in the corona. However, the choice of heating parameters in that study resulted in a solar wind with much lower densities and higher temperatures than what is observed in the corona. The density and temperature are crucial for the degree of coupling between helium and protons. We will attempt to tailor the heating so as to produce proton densities and temperatures that match coronal observations better, and we will study the coronal helium abundance for low helium heating rates in a more realistic corona.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFMSH31A1792B
- Keywords:
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- 7509 SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY / Corona;
- 7511 SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY / Coronal holes