Numerical simulations of the first harmonic kink mode of vertical oscillations of a solar coronal loop

摘要

Aims. We investigate impulsive excitation mechanisms of the first harmonic fast magnetoacoustic kink mode of vertical oscillations in a solar coronal loop, which is approximated by either a straight slab or a curved arcade slab. Methods. We solve numerically the full set of nonlinear ideal two-dimensional magnetohydrodynamic equations and analyze temporal and spatial wave signatures to infer characteristic features, such as waveperiods and node positions. Results. We show that an initial velocity pulse located off-center excites the first harmonic and fundamental modes, which result in a movement of the node around the loop apex. These results are verified by the analytical findings for an elastic string. Conclusions. Since the fundamental mode acquires more energy than its first harmonic, this explains why the latter is so rarely detected within a coronal loop.Key words: magnetohydrodynamics (MHD) - Sun: corona - Sun: oscillations