Decayless longitudinal oscillations of a solar filament maintained by quasi-periodic jets

Abstract

Context. As a ubiquitous phenomenon, large-amplitude longitudinal filament oscillations usually decay in 1–4 periods. Recently, we observed a decayless case of such oscillations in the corona. Aims. We try to understand the physical process that maintains the decayless oscillation of the filament. Methods. Multiwavelength imaging observations and magnetograms were collected to study the dynamics of the filament oscillation and its associated phenomena. To explain the decayless oscillations, we also performed one-dimensional hydrodynamic numerical simulations using the code MPI-AMRVAC. Results. In observations, the filament oscillates without decay with a period of 36.4 ± 0.3 min for almost 4 h before eruption. During oscillations, four quasi-periodic jets emanate from a magnetic cancellation site near the filament. The time interval between neighboring jets is ∼68.9 ± 1.0 min. Numerical simulations constrained by the observations reproduced the decayless longitudinal oscillations. However, it is surprising to find that the period of the decayless oscillations is not consistent with the pendulum model. Conclusions. We propose that the decayless longitudinal oscillations of the filament are maintained by quasi-periodic jets, which is verified by the hydrodynamic simulations. More importantly, it is found that, when it is driven by quasi-periodic jets, the period of the filament longitudinal oscillations also depends on the driving period of the jets, not on the pendulum period alone. With a parameter survey in simulations, we derived a formula by which the pendulum oscillation period can be derived using the observed period of decayless filament oscillations and the driving periods of jets.