The Detectability of Neon Fluorescence and Measurement of the Solar Photospheric Neon Abundance

Abstract

Monte Carlo calculations of the Ne K$\alpha$ line fluoresced by coronal x-rays and emitted near the temperature minimum region of the solar atmosphere have been employed to investigate the use of this feature to measure directly the solar photospheric Ne abundance. Though very weak, comparison with spectral line databases indicates that at plasma temperatures typical of the quiet Sun and cool active regions ($\le 2\times 10^6$ K) the line is isolated and unblended. A canonical solar chemical composition yields an equivalent width of $\sim 6$ mÅ(0.3 eV) when observed at heliocentric angles $\sim 0$. For a 1 arcmin field of view, photon fluxes at Earth are of order 0.2 ph s${}^{-1}$ for the quiet Sun, rendering the Ne K$\alpha$ fluorescent line a quite feasible means for determining the solar photospheric Ne content.

To appear in Astrophysical Journal Letters. 13 pages, 3 figures, 1 table

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