Observations of a solar flare and filament eruption in Lyman $mathsf{lpha}$ and X-rays

摘要

Context. Lis a strong chromospheric emission line, which has been relativelyrarely observed in flares. The Transition Region and Coronal Explorer(TRACE) has a broad ``Lyman''channel centered at 1216? used primarily at the beginning of themission. Asmall number of flares were observed in this channel. Aims. We aim to characterise the appearance and behaviour of aflare and filament ejection which occurred on8thSeptember1999 and was observed by TRACE in L,as well as by the YohkohSoft and Hard X-ray telescopes. We explore the flare energetics and itsspatial and temporal evolution. We have in mind the fact that the Llineis a target for the Extreme Ultraviolet Imaging telescope (EUI) whichhas been selected for the Solar Orbiter mission, as well as the LYOTtelescope on the proposed SMESE mission. Methods. We use imaging data from the TRACE 1216?, 1600? and 171? channels, and the Yohkoh hard and soft X-ray telescopes. Acorrection is applied to the TRACE data to obtain a better estimate of the pure Lsignature. The Lpower is obtained from a knowledge of the TRACE response function, andthe flare electron energy budget is estimated by interpreting Yohkoh/HXTemission in the context of the collisional thick target model. Results. We find that the Lflare is characterised by strong, compact footpoints (smaller than theUVribbons) which correlate well with HXRfootpoints. The Lpower radiated by the flare footpoints can be estimated, and is found to be on the order of 1026ergs-1at the peak. This is less than10% of the power inferred for theelectrons which generate the co-spatial HXRemission, and can thusreadily be provided by them. The early stages of the filament eruptionthat accompany the flare are also visible, and show a diffuse, roughlycircular spreading sheet-like morphology, with embedded denser blobs. Conclusions. On the basis of this observation, we conclude that flare and filament observations in the Llinewith the planned EUI and LYOT telescopes will provide valuable insightinto solar flare evolution and energetics, especially when accompaniedby HXR imaging and spectroscopy. Key words: Sun: activity - Sun: filaments - Sun: X-rays, gamma rays - Sun: coronal mass ejections (CMEs)