Core electron densities of coronal polar plumes

Abstract

The electron density in the cores of coronal polar plumes that is determined from observations will depend upon the assumed electron density distribution through the plume in a direction normal to its axis. Core electron densities obtained by Saito (1965) and by Newkirk and Harvey (1968) were derived using different assumed electron density profiles, and are not in agreement. We have re-discussed Saito's data using Newkirk and Harvey's electron density profile and find that the disagreement persists. Whether this indicates a true variation in electron density in plume cores cannot now be stated. Errors in the electron densities derived here may arise through errors in measuring the angles θ and α which enter into the analysis. While plausible variations in θ produce no appreciable errors in core electron density, plausible variations in α may introduce appreciable errors into the determinations of that quantity.