Signatures of transition region explosive events in hydrogen Ly-beta profiles

Abstract

We search for signatures of transition region explosive events (EEs) in hydrogen Ly-beta profiles. Two rasters made by the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) instrument on board SOHO in a quiet-Sun region and an equatorial coronal hole are selected for our study. Transition region explosive events are identified from profiles of C II 1037 Angstrom and O VI 1032 Angstrom, respectively. We compare Ly-beta profiles during EEs with those averaged in the entire quiet-Sun and coronal-hole regions. The relationship between the peak emission of Ly-beta profiles and the wing emission of C II and O VI during EEs is investigated. We find that the central part of Ly-beta profiles becomes more reversed and the distance of the two peaks becomes larger during EEs, both in the coronal hole and in the quiet Sun. The average Ly-beta profile of the EEs detected by C II has an obvious stronger blue peak. During EEs, there is a clear correlation between the increased peak emission of Ly-beta profiles and the enhanced wing emission of the C II and O VI lines. The correlation is more pronounced for the Ly-beta peaks and C II wings, and less significant for the Ly-beta blue peak and O VI blue wing. We also find that the Ly-beta profiles are more reversed in the coronal hole than in the quiet Sun. We suggest that the jets produced by EEs emit Doppler-shifted Ly-beta photons, causing enhanced emission at positions of the peaks of Ly-beta profiles. The more-reversed Ly-beta profiles confirm the presence of a larger opacity in the coronal hole than in the quiet Sun. The finding that EEs modify the Ly-beta line profile in QS and CHs implies that one should be careful in the modelling and interpretation of relevant observational data.

accepted for publication in Astronomy and Astrophysics; 8 pages, 2 tables, 5 figures

References in corpus (9)

• The nascent fast solar wind observed by EIS onboard Hinode
• Upflows in funnel-like legs of coronal magnetic loops
• The Ly-alpha profile and center-to-limb variation of the quiet Sun
• Solar transition region above sunspots
• Hydrogen Lyman-alpha and Lyman-beta spectral radiance profiles in the quiet Sun
• Signature of mass supply to quiet coronal loops
• The Ly<alpha> and Ly<beta> profiles in solar prominences and prominence fine structure
• Hydrogen Lyman-alpha and Lyman-beta radiances and profiles in polar coronal holes
• The SUMER Lyman-alpha line profile in quiescent prominences

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• Spectroscopic Case Studies of Four Long-duration Transition-region Explosive Events