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

Monte Carlo calculations of the Ne Kα 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. Although very weak, comparison with spectral line databases indicates that at plasma temperatures typical of the quiet Sun and cool active regions (<=2×10⁶ K) the line is isolated and unblended. A canonical solar chemical composition yields an equivalent width of ~6 mÅ (0.3 eV) when observed at heliocentric angles ~0. For a 1' field of view, photon fluxes at Earth are of order 0.2 photons s^-1 for the quiet Sun, rendering the Ne Kα fluorescent line a quite feasible means for determining the solar photospheric Ne content.