MHD WAVE DYNAMICS CLOSE TO A CURRENT SHEET

Using the WKB approximation, the propagation of fast magnetoacoustic w aves close to a Y-point of a current sheet is analyzed. When the prese nce of a small (of order epsilon), uniform magnetic field B-z parallel to the current, with the role of a perturbation, is taken into accoun t, weak chaos of the ray trajectories is found. The properties of the system are then analyzed by means of a mapping of the Poincare section . It is found that the region of stochasticity for very small epsilon fills almost the whole phase space, and decreases with increasing epsi lon.