The Funnel Geometry of Open Flux Tubes in the Low Solar Corona Constrained by O VI and Ne VIII Outflow

Abstract

We carry out model calculations to show that observed outflow velocities of order 7-10 km s^-1 of C IV and O VI ions, and 15-20 km s^-1 of Ne VIII ions, are not only consistent with models of the solar wind from coronal holes but also place unique constraints on the degree of flow tube expansion as well as the location of the expansion in the transition region/lower corona. We include nonequilibrium effects in the calculations and also show that ions and protons couple well in the line-forming region.