On the dynamics of solar polar plumes observed by SoHO/UVCS

Abstract

We investigate the plasma outflow in solar polar plumes by using SoHO/UVCS observations of May 2005. Despite the fact that data have been acquired more than ten years ago, UVCS spectral observations in the intermediate corona still represent a unique opportunity of studying the plasma dynamics at those heliocentric distances. The Doppler dimming technique is applied to the O VI doublet and H I Lyman- α spectral lines, to infer the outflow speed and the electron density in plumes and interplumes. Our aim is to, investigate if plumes, in the intermediate corona, are to be considered static structures or if they dynamically expand, contributing to the fast solar wind.