The D3 Emission of Prominences

The computed emission of H α and D₃ from an isothermal slab model prominence is shown to give agreement with observational data of Brück and Moss when the model has helium abundance one fifth that of hyd gen, thickness $$\lt2\times{10}^{4}$$ km, temperature between 1\cdot 1\times{10}^{4}$$ deg. K and $$2\cdot 0\times{10}^{4}$$ deg. K and electron concentration between $${10}^{10}\text{cm}^{-3}\,\text{to}\,5\times{10}^{10}\text{cm}^{-3}$$ . Some evidence has been found that the higher temperatures are generally associated with lower electron concentrations. Comparison of the present computations with earlier results obtained by the author from an analysis of the contour of the Hex emission of prominences shows that the ratio of the abundances of helium and hydrogen atoms in solar prominences lies in the range 0·12 to 0·4. As for H α , the self emission in D₃ is generally small compared with the diffusely reflected and transmitted component.