The Excitation and Damping of Transversal Coronal Loop Oscillations

Abstract

The excitation and damping of transversal coronal loop oscillations is studied using a simple line-tied one-dimensional model. The dynamics of the loop and the coronal environment is governed by the well-known Klein-Gordon equation, and so a localized disturbance (representing the effect of a solar flare) gives rise to a perturbation that undergoes dispersion as it propagates toward the loop. As a consequence, the loop oscillates at the external cutoff frequency, and its motion attenuates with time roughly as (with dense and wide loops having even Ϫ1/2 t stronger damping profiles). Hence, the damping of transversal loop oscillations is not related to any dissipation mechanism but is simply produced by the wake of the traveling disturbance. In addition, these damped oscillations are not related to the kink mode, although this mode can be excited after the attenuation process by the energy of the wave packet deposited in the loop.