Speaker
Description
First Name: Zheng
Last Name: Sun
Affiliation: Leibniz Institute for Astrophysics Potsdam
All Authors: Zheng Sun, Alexander G.M. Pietrow, Malcolm K. Druett, Hui Tian
Abstract: Flare ribbons map chromospheric footpoints where flare energy deposition occurs. These locations are associated with field aligned energy transport from the corona, that results from energy liberated during magnetic reconnection. Recent chromospheric observations have revealed fine-scale downflow structures above the expanding fronts of flare ribbons, referred to as riblets. In this study, we identify similar downflow structures in the extreme-ultraviolet (EUV) wavelength using high-resolution observations from Solar Orbiter/EUI. These EUV riblets appear as downward-propagating, bright, and thread-like structures. They exhibit typical velocities of ~100 km/s, lifetimes of ~15s, and lengths of ~1.6Mm. Based on their morphological and dynamical properties, we interpret these observed downflows as the EUV counterparts of the same fine structures that have previously been reported from chromospheric observations. This study provides clear imaging of ~1 MK downflows in the lower atmospheric footpoints of flare ribbon formation. We interpret these downflows as a result of (1) the energisation and subsequent compression of pre-existing chromospheric fibrils due to particle beams or (2) adiabatic or shock-driven compression induced by the downward-propagating plasma from the corona. These fine-scale EUV riblets provide a new diagnostic for probing the dynamics of magnetic reconnection and energy transport and deposition during solar flares.