The coronal convection

TL;DR

This study analyzes hydrogen Lyman emission in solar features, revealing how flows and magnetic fields influence line profiles and radiance, and introduces the concept of coronal convection as a fundamental mass transport process.

Contribution

It provides new observational insights into Lyman-alpha and Lyman-beta line asymmetries, linking them to solar flows and magnetic structures, and introduces the concept of coronal convection.

Findings

Higher opacity regions cluster in cell interiors.

Coronal hole spectra show deeper self reversals.

Opposite asymmetries in Lyman-alpha and Lyman-beta lines.

Abstract

We study the hydrogen Lyman emission in various solar features - now including Lyman-alpha observations free from geocoronal absorption - and investigate statistically the imprint of flows and of the magnetic field on the line profile and radiance distribution. As a new result, we found that in Lyman-alpha rasters locations with higher opacity cluster in the cell interior, while the network has a trend to flatter profiles. Even deeper self reversals and larger peak distances were found in coronal hole spectra. We also compare simultaneous Lyman-alpha and Lyman-beta profiles. There is an obvious correspondence between asymmetry and redshift for both lines, but, most surprisingly, the asymmetries of Lyman-alpha and Lyman-beta are opposite. We conclude that in both cases downflows determine the line profile, in case of Lyman-alpha by absorption and in the case of Ly-beta by emission. Our results show that the magnetically structured atmosphere plays a dominating role in the line formation and indicate the presence of a persisting downflow at both footpoints of closed loops. We claim that this is the manifestation of a fundamental mass transportation process, which Foukal back in 1978 introduced as the 'coronal convection'.