French, Ryan J;
Yu, Sijie;
Chen, Bin;
Shen, Chengcai;
Matthews, Sarah A;
(2024)
Doppler signature of a possible termination shock in an off-limb solar flare.
Monthly Notices of the Royal Astronomical Society
, 528
(4)
pp. 6836-6844.
10.1093/mnras/stae430.
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Abstract
We report striking Doppler velocity gradients observed during the well-observed 2017 September 10 solar flare, and argue that they are consistent with the presence of an above-the-looptop termination shock beneath the flare current sheet. Observations from the Hinode Extreme-ultraviolet Imaging Spectrometer measure plasma sheet Doppler shifts up to 35 km s−1 during the late-phase of the event. By comparing these line-of-sight flows with plane-of-sky (POS) measurements, we calculate total velocity downflows of 200+ km s−1, orientated ≈6–10° out of the POS. The observed velocities drop rapidly at the base of the hot plasma sheet seen in extreme ultraviolet, consistent with simulated velocity profiles predicted by our 2.5D magnetohydrodynamics model that features a termination shock at the same location. Finally, the striking velocity deceleration aligns spatially with the suppression of Fe XXIV non-thermal velocities, and a 35–50 keV hard X-ray looptop source observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager. Together, these observations are consistent with the presence of a possible termination shock within the X8.2-class solar flare.
| Type: | Article |
|---|---|
| Title: | Doppler signature of a possible termination shock in an off-limb solar flare |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1093/mnras/stae430 |
| Publisher version: | http://dx.doi.org/10.1093/mnras/stae430 |
| Language: | English |
| Additional information: | Copyright © 2024 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. |
| Keywords: | Sun: flares, Sun: corona, Sun: UV radiation, Sun: X-rays, gamma-rays, magnetic reconnection, techniques: imaging spectroscopy |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10188164 |
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