Emerging active regions on the sun and the photospheric abundance of neon

Early work on Skylab spectroheliograms showed that deep-lying impulsive flares and newly emerged active regions showed a high relative abundance of neon, thought to be representative of the unknown neon abundance in the underlying photosphere. In pursuit of this idea a survey of emerging magnetic flux sequences on Skylab spectroheliograms (300-600 Angstrom) has been made, and from these the Ne/Mg abundance ratio has been derived by combining plots of the ion differential emission measures, From the initial phase of five emerging flux sequences a stable value of the Ne/Mg abundance ratio equal to 3.16 +/- 0.07 has been determined. Normalizing this to the well-determined abundance of magnesium, the photospheric abundance of neon is log Neon = 8.08 +/- 0.06, log H = 12. This result is compared with previous estimates which used ''local galactic values'' as a proxy for the unknown neon abundance. The present results are also compared with a slightly larger Ne/Mg ratio of 3.6 +/- 0.4 (log Neon = 8.14) observed in a deep-lying impulsive flare, also thought to expose a sample of photospheric material.