Polar Plumes and Inter-plume regions as observed by SUMER on SOHO

Abstract

We present observations of O vi 1032 Å line profiles obtained with the SUMER instrument on SOHO extending from the solar disk to 1.5 R ⊙ above the limb in the north polar coronal hole. Variations of the intensity and linewidth in the polar plume and inter-plume regions are investigated. We find an anti-correlation between the intensity and the linewidth in the plume and inter-plume regions with detailed plume structures been seen out to 1.5 R ⊙. Possible implications regarding the magnetic topologies of these two regions and related heating mechanisms are discussed. The O vi linewidth measurements are combined with UVCS output to provide an overview of its variations with height extending up to 3.5 R ⊙. We find a linear increase of the linewidth from 1 to 1.2 R ⊙, then a plateau followed by a sharp increase around 1.5 R ⊙.