STOCHASTIC PROPERTIES OF THE MAGNETIC-FIELD LINES IN THE PRESENCE OF CURRENT SHEETS (VOL 63, PG 284, 1996)

The process of separatrix broadening under the action of periodic pert urbations is investigated in the case when the equilibrium magnetic co nfiguration contains current sheets. The change of the magnetic field topology due to the presence of current sheets is discussed, and compa red to the case of the standard figure-eight separatrix. In this case, the Hamiltonian structure of the magnetic field separatrix modifies d ue to the presence of Y-points instead of X-points. Contrary to the ca se of X-points, the period of the motion is always finite, and experie nces a finite jump when the trajectory in the phase plane crosses the separatrix. This fact leads to the appearance of a stochastic layer. T his phenomenon is of relevance in the analysis of the processes arisin g in the nonlinear stage of the m = 1 mode instability in a tokamak ma gnetic field.