Nonphotospheric Abundances in a Solar Active Region

Abstract

Element abundances have been determined for a solar active region observed to have a highly nonphotospheric Ne/Mg abundance ratio associated with an open magnetic field. This active region is an example of a class of relatively inconspicuous features with open magnetic fields which contrast with brighter, more compact emission regions with less anomalous abundance ratios. The study is based on images of the active region in Ne VI, VII, Mg VI-VIII, Na VIII, Si VIII, and Ca VIII, IX photographed in the 300-600 A range by the NRL spectroheliograph on Skylab. Element abundances relative to magnesium were determined by combining plots of the ion differential emission measures