On the excitation of trapped and leaky modes in coronal slabs

Departament de Física, Universitat de les Illes Balears, 07122 Palma de Mallorca, Spain e-mail: [jaume.terradas;ramon.oliver;dfsjlb0]@uib.es

Received: 5 April 2005
Accepted: 23 June 2005

Abstract

We study the excitation of fast waves in solar coronal loops modeled as smoothed, dense plasma slabs in a uniform magnetic field. We analyse the features of the trapped and leaky modes which result from an initial disturbance generated in the loop. By solving the time-dependent problem we find that the stationary state of the slab motion is described by the trapped normal modes and that the transient between the initial and the stationary phase is dominated by wave leakage. The period and duration of this transient (what we call the impulsive leaky phase) are in perfect agreement with the corresponding values of leaky modes calculated from the normal mode analysis.