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IRIS observations of the Mg ii h and k lines during a solar flare

Fletcher, L.; Qiu, J.; Simões, P. J. A. +1 more

The bulk of the radiative output of a solar flare is emitted from the chromosphere, which produces enhancements in the optical and UV continuum, and in many lines, both optically thick and thin. We have, until very recently, lacked observations of two of the strongest of these lines: the Mg ii h and k resonance lines. We present a detailed study o…

A steady-state supersonic downflow in the transition region above a sunspot umbra

Andretta, Vincenzo; Straus, Thomas; Fleck, Bernhard

We investigate a small-scale (~1.5 Mm along the slit), supersonic downflow of about 90 km s^-1 in the transition region above the lightbridged sunspot umbra in AR 11836. The observations were obtained with the Interface Region Spectrograph (IRIS) on 2013 September 2 from 16:40 to 17:59 UT. The downflow shows up as redshifted "satellite" …