Magnetic Field Configuration of a Quiescent Prominence Revealed by Large-amplitude Longitudinal Oscillations in End-view Observations

Abstract Prominence seismology, applied to large-amplitude longitudinal oscillations, is used to indirectly diagnose the geometry and strength of the magnetic fields inside the prominence. In this paper, combining imaging and spectroscopic data, the magnetic field configuration of a quiescent prominence is revealed by large-amplitude longitudinal oscillations observed in end view on 2023 December 4. In particular, the prominence oscillation involved blueshift velocities in Dopplergrams and horizontal motions in extreme-ultraviolet images. Originally, the prominence oscillation was triggered by the collision and heating of an adjoining hot structure associated with two coronal jets. The oscillation involved two groups of signals with similar oscillatory parameters, a three-dimensional (3D) initial amplitude of ∼40 Mm and a 3D velocity amplitude of ∼48 km s −1 , both lasting for ∼4 cycles with a period of ∼77 minutes, with a phase difference of ∼ π /8. The angle between the 3D velocities and the prominence axis ranges from 10 ∘ to 30 ∘ . Two methods, utilizing time–distance diagrams and velocity fields, are employed to calculate the curvature radius of magnetic dips supporting the prominence materials. Both methods yield similar value ranges and trends from the bottom to the top of magnetic dips, with the curvature radius increasing from ∼90 Mm to ∼220 Mm, then decreasing to ∼10 Mm, with transverse magnetic field strength ≥25 Gauss. From this, the realistic 3D geometry of the prominence magnetic dips is determined to be sinusoidal. To the best of our knowledge, we present the first accurate calculation of the 3D curvature radius and geometry of the prominence magnetic dips based on longitudinal oscillatory motions.