Numerical simulations of large-amplitude oscillations in flux rope solar prominences

Abstract

Context. Large-amplitude oscillations (LAOs) of solar prominences are a very spectacular, but poorly understood, phenomena. These motions have amplitudes larger than 10 km s−1 and can be triggered by the external perturbations such as Moreton or EIT waves. Aims. Our aim is to analyze the properties of LAOs using realistic prominence models and the triggering mechanism by external disturbances. Methods. We performed time-dependent numerical simulations of LAOs using a magnetic flux rope model with the two values of shear angle and density contrast. We studied the internal modes of the prominence using horizontal and vertical triggering. In addition, we used perturbation that arrives from outside to understand how such external disturbance can produce LAOs. Results. The period of longitudinal oscillations and its behavior with height show good agreement with the pendulum model. The period of the transverse oscillations remains constant with height, suggesting a global normal mode. The transverse oscillations typically have shorter periods than longitudinal oscillations. Conclusions. The periods of the longitudinal and transverse oscillations show only weak dependence on the shear angle of the magnetic structure and prominence density contrast. The external disturbance perturbs the flux rope exciting oscillations of both polarizations. Their properties are a mixture of those excited by purely horizontal and vertical driving.