Impulsively Excited Quasiperiodic Fast-propagating Waves in the Solar Corona

Shi Mijie; Nakariakov Valery M.; Li Bo; Guo Mingzhe

Quasiperiodic fast-propagating (QFP) waves excited by an impulsive, spatially localized velocity perturbation in a curved coronal loop are investigated with three-dimensional numerical simulations. The equilibrium consists of a density-enhanced loop embedded in a magnetic arcade. The initial perturbation is a velocity pulse with either sausage symmetry or kink symmetry (vertically or horizontally polarized), applied near one loop footpoint. Fast magnetoacoustic wave trains guided along the loop (i.e., trapped fast wave trains) arise in both cases due to waveguide dispersion. However, in the kink case, the trapped wave trains are less pronounced than in the sausage case because kink modes exhibit weaker dispersion and weaker compression. Leaky fast magnetoacoustic wave trains also form for all considered symmetries. In the sausage case, the leaky-wave density perturbation is symmetric about the loop plane; in the kink cases it is either symmetric or antisymmetric, depending on whether the excitation is vertically or horizontally polarized. Forward modelling of the observational manifestation of the waves in the optically thin regime shows that trapped wave trains are detectable for all examined viewing angles, whereas leaky-wave signals can be very faint for certain viewing directions. These results support the notion that coronal QFP waves can be excited by a velocity pulse and suggest that the infrequent detection of broad QFP waves may stem from line-of-sight integration effects.