X-ray and Spectral UV Observations of Periodic Pulsations in a Solar Flare Fan/Looptop

TL;DR

This study reports on simultaneous X-ray and UV observations of highly periodic pulsations in a solar flare's looptop, revealing insights into magnetic tuning fork oscillations and betatron acceleration through innovative analysis methods.

Contribution

It introduces the 'Sliding Raster Method' (SliRM) for enhanced temporal analysis of spectrometer data, linking observed pulsations to magnetic and acceleration processes in solar flares.

Findings

Oscillations are highly periodic, lasting over 5 minutes.

Oscillations are attributed to magnetic tuning fork and betatron acceleration.

New analysis method (SliRM) improves temporal resolution of spectrometer data.

Abstract

We present simultaneous X-ray and spectral ultraviolet (UV) observations of strikingly-coherent oscillations in emission from a coronal looptop and fan structure, during the impulsive phase of a long-duration M-class solar flare. The 50 s oscillations are observed near in-phase by Solar Orbiter/STIX, GOES, and IRIS Fe XXI intensity, Doppler and non-thermal velocity. For over 5 minutes of their approximate 35 minute duration, the oscillations are so periodic (2-sigma above the power law background), that they are better described as 'periodic pulsations' than the more-widely documented 'quasi-periodic pulsations' often observed during solar flares. By combining time-series analysis of the the multi-instrument datasets with comparison to MHD simulations, we attribute the oscillations to the magnetic tuning fork in the flare looptop-fan region, and betatron acceleration within the lower-altitude flare loops. These interpretations are possible due to the introduced 'Sliding Raster Method' (SliRM) for analysis of slit spectrometer (e.g. IRIS) raster data, to increase the temporal cadence of the observations at the expense of spatial information.