Spectroscopic Observations of Solar Flare Pulsations Driven by Oscillatory Magnetic Reconnection

Solar and stellar flares often exhibit oscillations, or quasi-periodic pulsations (QPPs), across the electromagnetic spectrum. While magnetic field reconnection drives these events, it remains to be determined whether oscillatory reconnection causes the quasi-periodicity, or if waves drive or mediate this process. Exploiting coordinated observations from NASA’s Interface Region Imaging Spectrograph and the Swedish 1m Solar Telescope, this work presents novel spectroscopic observations of QPPs in a solar flare at high-temporal (< 1s) and high-spatial (≈60 km) resolution. Downward velocities in the flare ribbon show synchronized oscillations at different atmospheric layers with a period of ≈35s. These velocities correlate with hard X-ray emissions, indicating a modulated deposition of accelerated electrons in the chromosphere as the driver. By negating MHD sausage modes as the modulator, we demonstrate that repeated reconnection drives the QPPs. These results advance our understanding of magnetic reconnection in flares and its role in driving oscillatory signals.