Fine-scale downflows above flare ribbons captured by Solar Orbiter/EUI

¹ School of Earth and Space Sciences, Peking University, Beijing 100871, PR China
² State Key Laboratory of Solar Activity and Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing 100190, PR China
³ Leibniz Institute for Astrophysics Potsdam, An der Sternwarte 16, Potsdam 14482, Germany
⁴ Plasma Dynamics Group, School of Electrical and Electronic Engineering, University of Sheffield, Sheffield, S1 3JD, UK
⁵ Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Potsdam-Golm, Germany
⁶ State Key Laboratory of Solar Activity and Space Weather, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, PR China
⁷ Centre for Mathematical Plasma Astrophysics, KU Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium

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Received: 15 March 2026
Accepted: 16 June 2026

Abstract

In solar flares, 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 in the Hα and Hβ bands have revealed fine-scale downflow structures above 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 fine-scale downflows appear as downward-propagating, bright, and thread-like structures. They exhibit typical velocities of ~100 km s⁻¹, lifetimes of ~15 s, and lengths of ~1.6 Mm. Based on their morphological and dynamical properties, we interpret these observed downflows as the EUV counterparts of the riblets that have previously been reported from chromospheric observations. This study presents EUV imaging of ~10⁶ K downflows above flare ribbons. 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 tool for probing the dynamics of magnetic reconnection as well as energy transport and deposition during solar flares.