Searching for Spectroscopic Signs of Termination Shocks in Solar Flares
Abstract
The standard flare model predicts the presence of a termination shock located above the flare loop tops, however terminations shocks have not yet been well observed. We analyze flare observations by the Interface Region Imaging Spectrograph (IRIS), which provides cotemporal UV imaging and spectral data. Specifically, we study plasma emissions in the Fe XXI line, formed at the very hot plasma temperatures in flares (> 10 MK). Imaging observations that point to shocks include fast hot reconnection downflows above the loop tops and localized dense, bright plasma at the loop tops; spectral signatures that suggest shocks in the locality of the loop tops include redshifts and nonthermal broadening of the Fe XXI line. We identify possibly significant redshifts in some on-disk flare events observed by IRIS. Redshifts are observed in the vicinity of the bright loop top source that is thought to coincide with the site of the shock. In these events, the Fe XXI emissions at the time of the redshifted structures are dominated by at the at-rest components. The much more less intense redshifted components are broader, with velocities of 200 km/s. The spatial location of these shifts might indicate plasma motions and speeds indicative of termination shocks. This work is supported by the NSF-REU solar physics program at SAO, grant number AGS-1560313, and by NASA Grant NNX15AJ93G. Keywords: Solar flares, Solar magnetic reconnection, Termination shocks
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFMSH51C2501G
- Keywords:
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- 7599 General or miscellaneous;
- SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY;
- 7899 General or miscellaneous;
- SPACE PLASMA PHYSICS;
- 7999 General or miscellaneous;
- SPACE WEATHER