Automatic detection of Flare Ribbon Fine Structures as Proxies for Plasmoid Dynamics in Flare Reconnection

Flare ribbons often display fine structures along their fronts that are commonly interpreted as signatures of intermittent reconnection dynamics including plasmoid formation in the flare current sheet. We introduce an automated method that detects and tracks the spiral- and wave-like imprints of these structures and as a proof of concept apply it to maps of magnetic field-line length from a high-resolution 3D eruptive-flare simulation. The workflow applies the correlation-dimension method, density-based clustering, and a minimum-area ellipse fit to summarise each feature. We show that across the simulated flare, the detected spirals remain locked to the ribbon's outward motion while drifting coherently along the ribbon. The two ribbons show opposite along-ribbon drift and motion away from their hooks in accordance with theoretical expectations, with instantaneous speeds of 10-800 km s 1, all well below the local surface Alfven speed. Occurrence, lifetimes, and mean magnetic flux of the features peak during the impulsive phase. The distribution of per-spiral mean unsigned flux shows a scale-free tail above roughly 6x10 18 Mx with a power-law exponent near 3.4. Together, these results show that bursty, plasmoid-mediated flare reconnection leaves a clear, measurable signature on the flare ribbons. The method provides a practical surface diagnostic of ribbon fine structure that can potentially be used to inform our understanding of three-dimensional magnetic reconnection in the flare current sheet.