Off-Limb Electron Density Variation
In order to develope models, one need physical parameters such as the electron temperature and density. For Ne we measure the variation of the electron density using line pairs from Si VIII and Si IX, plus up-to-date atomic data from QUB.

Off-limb electron density variation

From the combined datasets we find a radial dependence of the electron density, in the range 1-2 solar radii  as r^{-8}, from 2-4R as r^{-4} and then as r^{-2}. Combining with the line width measurement, the data suggests that the MHD waves are important for heating the corona (as found from the oscillation data).