QPPs

Spectroscopic Observations of Solar Flare Pulsations Driven by Oscillatory Magnetic Reconnection

This study utilized a coordination observation campaign between IRIS and the Swedish Solar Telescope, providing a high-cadence (~1s) and high-resolution (~60km) data set. We found that quasi-periodic pulsations (QPPs) in chromospheric redshifts, a signature of flare energy release in the lower solar atmosphere, were correlated with hard X-rays from the same region. This correlation suggests that these redshifts are caused by modulated accelerated electron deposition.

The oscillations in the Si IV 1402.77 Å line were found using a multi-Gaussian spectral fitting routine, where we focused on the primary, blue Gaussian:

Spectroscopic analysis of the Ca II k line over the flare region found that the QPPs were also spatially distributed across the flare ribbon, showing a distribution of ~34 seconds. The uniformity of this distribution provides evidence for a centralized mechanism driving the QPPs. In conjunction with the HXR oscillations, we found the likelyest candidate that explains these observations is electron acceleration modulated by quasi-periodic reconnection.