The behaviour of impurities out of coronal equilibrium

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Abstract
The behaviour of a range of impurities, in the presence of neutral thermal hydrogen atoms, is examined analytically for non-equilibrium coronal conditions. The time, tau ss, required for an impurity species to establish equilibrium is found to be sensitively dependent on the plasma electron temperature and is strongly correlated with the ionisation state distribution at equilibrium. Peak values of ne tau ss approximately=2*1018 m-3 s are found. The temporal and ensemble averaged calculations of the impurity charge states and radiation power which are presented here allow for the treatment of impurities without recourse to lengthy computation. The impurities (carbon, oxygen, iron and molybdenum) are considered in terms of the electron temperature, the fractional neutral hydrogen concentration, and the time spent by the impurities in the plasma.