LOCAL WAVES IN A MAGNETIC ARCADE EMBEDDED IN THE SOLAR CORONA

We consider a particular type of a magnetic non potential 2D arcade wh ich is in static equilibrium with the ambient, isothermal atmosphere. By applying linear 2D perturbations to it, we obtain the relevant MI-I D equations that describe the resulting wave velocity field, which can be reduced to a set of two coupled second order differential equation s for the velocity components parallel and normal to the magnetic surf aces. Those equations have been solved analytically in local approxima tion and under the assumption of constant Alfven speed. The results sh ow the existence of a surface wave, in addition to the propagating wav es (the fast and the slow mode), when a single boundary is present. Th e slow mode cannot escape the arcade while the fast made can leave it provided the speed of sound is not negligible if compared with the Alf ven speed. In the case of two boundaries, i.e. for a magnetic arch, th e obtained wave behaviour resembles that for a horizontal slab.