Doppler signature of a possible termination shock in an off-limb solar flare

Document Type

Article

Publication Date

3-1-2024

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.

Identifier

85185845244 (Scopus)

Publication Title

Monthly Notices of the Royal Astronomical Society

External Full Text Location

https://doi.org/10.1093/mnras/stae430

e-ISSN

13652966

ISSN

00358711

First Page

6836

Last Page

6844

Issue

4

Volume

528

Grant

2108438

Fund Ref

National Science Foundation

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