IMPULSIVELY GENERATED MHD WAVES IN A CORONAL PLASMA

Impulsively generated nonlinear waves in smoothed slabs of arbitrary b eta plasma are studied numerically by an application of the code that uses the flux corrected transport method. Numerical results show that a total reflection which occurs in the region of a low Alfven speed le ads to trapped waves. These waves propagate along the slab and exhibit periodic, quasi-periodic and decay phases. As a consequence of a diff erence in the waves speeds time signatures of slow and fast waves are shifted in time. An interaction between these waves can generate a lon ger lasting and complex quasi-periodic phase of the fast wave. A slow standing wave which is initially generated in a closed slab can excite another standing wave at the x-point of the same local cusp speed. At early stages of its time evolution the excited wave possesses twice s maller wavelength than the original standing wave. Later on both waves have the same wavelength. These waves communicate themselves by a fas t wave which is forced by the original slow wave.