Deflection of a filament eruption with three parallel flare ribbons via reconnection at an X-point

¹ School of Astronomy and Space Science and Key Laboratory of Modern Astronomy and Astrophysics, Nanjing University, Nanjing 210023, China
² Centre for Mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B, B-3001 Leuven, Belgium

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 3 November 2025
Accepted: 26 March 2026

Abstract

Context. On 2024 May 6, Active Region 13663 produced an X4.5-class flare associated with a filament eruption that exhibited remarkable rotation and deflection dynamics.

Aims. We investigated two key aspects of this event: the formation mechanisms of the complex flare ribbon structures and the physical drivers behind the observed filament deflection.

Methods. We conducted a data-constrained magnetohydrodynamic simulation using the zero-beta approximation to reconstruct the filament’s evolution. Through detailed analysis of quasi-separatrix layers (QSLs) and their comparison with observed flare ribbons, we established crucial connections between magnetic topology and flare morphology.

Results. Our simulation successfully reproduces key observational features of the eruption. We also connect the flare ribbon morphology with calculated QSLs. Finally, we find filament deflection resulting from localized reconnection at the X-point, as evidenced by Lorentz force decomposition.

Conclusions. We demonstrate that reconnection above two current channels of opposite helicity governs the eruption dynamics, with magnetic pressure gradients driving flux rope deflection and a magnetic tension force simultaneously restraining arcade ascent. The event features a “sandwich” magnetic configuration that includes double parallel polarity inversion lines with a strong shear component. We suggest that this particular configuration could serve as a plausible formation mechanism for the observed parallel three-ribbon structure. In addition, the evolution of QSLs and flare ribbons provides clear evidence of reconnection between two flux ropes.