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The effect of a non-maxwellian electron distribution on oxygen and iron ionization balances in the solar corona
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The effect of a non-maxwellian electron distribution on oxygen and iron ionization balances in the solar corona

S. P Owocki and J. D Scudder
The Astrophysical journal, Vol.270(2), pp.758-768
1983
DOI: 10.1086/161167

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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.
Astronomy Solar Physics Corona. Coronal loops, streamers, and holes Earth, ocean, space Exact sciences and technology Solar system

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