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Abstract: We search for signatures of transition region explosive events EEs inhydrogen Ly-beta profiles. Two rasters made by the SUMER Solar UltravioletMeasurements of Emitted Radiation instrument on board SOHO in a quiet-Sunregion and an equatorial coronal hole are selected for our study. Transitionregion explosive events are identified from profiles of C II 1037 Angstrom andO VI 1032 Angstrom, respectively. We compare Ly-beta profiles during EEs withthose averaged in the entire quiet-Sun and coronal-hole regions. Therelationship between the peak emission of Ly-beta profiles and the wingemission of C II and O VI during EEs is investigated. We find that the centralpart of Ly-beta profiles becomes more reversed and the distance of the twopeaks 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 strongerblue peak. During EEs, there is a clear correlation between the increased peakemission of Ly-beta profiles and the enhanced wing emission of the C II and OVI lines. The correlation is more pronounced for the Ly-beta peaks and C IIwings, and less significant for the Ly-beta blue peak and O VI blue wing. Wealso find that the Ly-beta profiles are more reversed in the coronal hole thanin the quiet Sun. We suggest that the jets produced by EEs emit Doppler-shiftedLy-beta photons, causing enhanced emission at positions of the peaks of Ly-betaprofiles. The more-reversed Ly-beta profiles confirm the presence of a largeropacity in the coronal hole than in the quiet Sun. The finding that EEs modifythe Ly-beta line profile in QS and CHs implies that one should be careful inthe modelling and interpretation of relevant observational data.



Autor: M. Zhang, L.-D. Xia, H. Tian, Y. Chen

Fuente: https://arxiv.org/







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