Helium-like Line Emission from Coronal Features

Abstract

SINCE Gabriel and Jordan1 proposed the theory relating the relative intensity of the inter-system (3P–1S0) and forbidden (3S1 – 1S0) lines of helium-like ions to the electron density of the emitting volume there has been growing interest in using this type of information to determine electron densities in the solar corona2–5. We present here the preliminary results of a rocket experiment designed to study the OVII and NeIX line emission from discrete coronal features. These results indicate that electron densities in normal, non-flare, coronal features are below the low density limits (6 × 109 and 1 × 1011 cm−3 respectively) given by Freeman et al.5 for these particular ions.