Hydrogen Lyman emission through the solar cycle

TL;DR

This study analyzes hydrogen Lyman-alpha emission variations over the solar cycle using high-resolution observations from SUMER, revealing that changes in solar features' radiance and distribution explain irradiance variations.

Contribution

It provides the first high-resolution on-disk observations of hydrogen Ly-alpha emission in various solar features, linking magnetic fields to line profile and radiance distribution changes.

Findings

Cycle variation in Ly-alpha irradiance is due to changes in solar feature distribution.

High-resolution SUMER data reveals magnetic field influence on line profiles.

Comparison of Ly-alpha and Ly-beta profiles enhances understanding of solar emission processes.

Abstract

We present observations and results of radiance and irradiance studies completed by SoHO-SUMER during the past solar cycle. We find that the cycle variation in Ly-alpha irradiance as observed by e.g. UARS-SOLSTICE can not be explained by quiet sun radiance data, and conclude that the explanation must be related to differences in the Ly-alpha radiance of various solar features and changes in their fractional distribution over the solar cycle. Consequently, we studied the emission of the hydrogen Ly-alpha line in various solar features - for the first time observed by SUMER on disk in full resolution - to investigate the imprint of the magnetic field on line profile and radiance distribution. We also compare quasi-simultaneous Ly-alpha and Ly-beta line profiles. Such high-resolution observations - not hampered by geocoronal absorption - have never been completed before.