Impulsively Generated Wave Trains in a Solar Coronal Loop

摘要

Impulsively generated fast magnetoacoustic wave trains in a solar coronal loop are numerically studied. The problem is considered as 2-D in space, and for the description, the full set of magnetohydrodynamic (MHD) equations is used. The numerical solution of the MHD equations is performed by means of the Lax–Wendroff algorithm on a uniformly structured mesh. The wavelet analysis of the obtained wave trains shows out the typical tadpole shapes, i.e., a narrow tail followed by a broadband head. In this paper, we discuss the propagation speed and periods of the wave trains as well as the shapes of the tadpoles in dependence on the plasma beta parameter. These studies are very important in connection with the observations because the tadpole signatures, firstly discovered during the solar eclipse in 1999 by the SECIS instrument, have been recently recognized also in decimetric type IV radio events by the Ondřejov radiospectrograph.