The effect of a non-Maxwellian electron distribution on oxygen and iron ionization balances in the solar corona
Abstract
Analytic expressions are derived for ionization and recombination rates in a parameterized non-Maxwellian electron velocity distribution with an enhanced high-energy tail. These expressions are then used in investigating the effect of such an enhancement in the high-energy tail of the coronal electron velocity distribution on the oxygen and iron ionization balances, O(+6) - O(+7) and Fe(+11) - Fe(+12). Relative to a Maxwellian of the same mean electron energy, the degree of ionization allowed by such a distribution is found to be either unchanged or slightly decreased for iron but often substantially increased for oxygen. The greater sensitivity of oxygen ionization balance to the high-energy distribution tail derives from the higher oxygen ionization threshold energy. It is noted that the electron temperature inferred from a measurement of the oxygen ionization ratio, O(+6)/O(+7), could indeed overestimate the actual coronal electron temperature by nearly 10 to the 6th K if the coronal electron distribution is incorrectly assumed to be Maxwellian.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 1983
- DOI:
- 10.1086/161167
- Bibcode:
- 1983ApJ...270..758O
- Keywords:
-
- Electron Distribution;
- Ionization;
- Solar Corona;
- Electron Energy;
- Iron;
- Oxygen Ions;
- Radiative Recombination;
- Velocity Distribution;
- Solar Physics