Spatiotemporal evolution of UV pulsations and their connection to 3D magnetic reconnection and particle acceleration

TL;DR

This study investigates the origin and dynamics of quasi-periodic pulsations in a solar flare, linking UV and X-ray emissions to magnetic reconnection processes and particle acceleration, revealing spatial and temporal variability.

Contribution

It provides new insights into the spatial origin and driving mechanisms of UV pulsations, emphasizing the role of slipping reconnection in an asymmetric magnetic environment.

Findings

UV pulsations correlate with HXR emissions from flare kernels.

Different regions show varied pulsation characteristics.

Magnetic reconnection propagation influences pulsation evolution.

Abstract

Quasi-periodic pulsations (QPPs) are a common feature of impulsive solar flare emissions, yet their driving mechanism(s) remain unresolved. We study long-period (3.4 min) QPPs in the M3.7 flare on Feb 24, 2023, using SDO/AIA and Solar Orbiter/STIX to pinpoint their source and driver. We analyzed UV and HXR emissions from four subregions covering the flare ribbons and footpoints of the erupting filament. We find the QPP characteristics varied significantly across these regions. The strongest UV pulsations, which correlated strongly with HXR emissions, originated from a sequence of flare kernels at the expanding front of the southern flare ribbon. In contrast, another expanding ribbon front showed no pulsations. The spatial coincidence of UV and HXR sources points to non-thermal electrons as a common driver, with the HXR spectrum showing a soft-hard-soft evolution matching the pulsation timescale. We also observed UV pulsations from plasma injections into a separate filament channel, distinct from the main flare kernels. Our results suggest that the spatiotemporal evolution of the pulsations is driven by the propagation of magnetic reconnection in an asymmetric geometry. We propose that slipping reconnection along quasi-separatrix layers is key to generating and moving the UV kernels, potentially modulated by another time-varying process.