Velocities and Linewidths in the Network and Cell Interiors of a Polar Coronal Hole, Compared with Quiet Sun

TL;DR

This study compares Doppler velocities and linewidths in the network and cell interiors of a polar coronal hole and quiet Sun, revealing regional differences and correlations across different atmospheric heights.

Contribution

It provides detailed measurements of velocity and linewidth variations between network and cell regions in coronal holes and quiet Sun, using SOHO/CDS data across multiple emission lines.

Findings

Broader velocity and linewidth histograms in cell interiors.

Network has larger linewidths than cells in certain lines.

Correlations between velocity and linewidth vary with height and region.

Abstract

The relative Doppler velocities and linewidths in a polar coronal hole and the nearby quiet-Sun region have been obtained from the {\it Solar and Heliospheric Observatory} (SOHO)/{\it Coronal Diagnostic Spectrometer} (CDS) observations using emission lines originating at different heights in the solar atmosphere from the lower transition region (TR) to the low solar corona. The observed region is separated into the network and the cell interior and the behavior of the above parameters were examined in the different regions. It has been found that the histograms of Doppler velocity and width are generally broader in the cell interior as compared to the network. The histograms of Doppler velocities of the network and cell interior do not show significant difference in most cases. However, in the case of the quiet Sun, the Doppler velocities of the cell interior are more blueshifted than those of the network for the lowermost line He {\sc ii} 304 {\AA}, and an opposite behavior is seen for the uppermost line Mg {\sc ix} 368 {\AA}. The histograms of line width show that the network--cell difference is more prominent in the coronal hole. The network has significantly larger linewidth than the cell interior for the lowermost TR line He {\sc ii} 304 {\AA} for the quiet Sun. For coronal hole, this is true for the three lower TR lines He {\sc ii} 304 {\AA}, O {\sc iii} 599 {\AA}, and O {\sc v} 630 {\AA}. Also obtained are the correlations between the relative Doppler velocity and the width. A mild positive correlation is found for the lowermost transition region line He {\sc ii} 304 {\AA} which further decreases or become insignificant for the intermediate lines. For the low coronal line, Mg {\sc ix} 368 {\AA}, the correlation becomes strongly negative.