AbstractUltraviolet (HST, FUSE) and extreme-ultraviolet (EUVE) observations of stellar coronae and flare-related activity are reviewed, with particular attention being devoted to the coronas information that is obtainable in the ultraviolet but not from the X-ray region. The coronas temperature, density, and emission measure distributions of active stars are significantly different from quiescent solar coronas conditions, thus allowing broader study of the underlying physical processes. Stellar coronae are magnetically-confined plasmas typically with substantially higher heating rates and temperatures than encountered in the Quiet Sun. Conditions are similar to solar flares but the question of the flare contribution during “quiescence” is still unresolved. The properties of stellar flares observed in long EUVE monitoring observations and the relationship between. events seen in different atmospheric regions are discussed. UV coronas forbidden lines, e.g. Fe XXI 13541 , Fe XII 1242, 1349 Å , Fe XVIII 975 Å, and Fe XIX 1118 Å are commonly detected in active dwarfs and giants; these lines currently provide the only resolved spectroscopic diagnostics of conditions within stellar coronae. The UV coronas lines generally have widths consistent with thermal broadening and are unshifted. Currently only tantalising glimpses of flare-related motions have been detected.


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    Titel :

    UV and EUV observations of stellar coronal structure and activity


    Beteiligte:

    Erschienen in:

    Advances in Space Research ; 32 , 6 ; 977-984


    Erscheinungsdatum :

    2003-02-07


    Format / Umfang :

    8 pages




    Medientyp :

    Aufsatz (Zeitschrift)


    Format :

    Elektronische Ressource


    Sprache :

    Englisch



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