In this paper we analyze the dynamics of single particle motion in the parabolic field model of the geomagnetotail using both numerical and analytical methods. We focus on the topology of the Poincar¿ surface of section and its evolution, when the field lines are strongly curved (&kgr;<0.53). The stochastic region is classified into RB subcells and fingers. Diffusion of intersections in RB subcells and fingers is different because the subcells and fingers correspond to destructed islands and destructed separatrices, respectively. Phenomena like differential memory and enhanced trapping and escaping are results of these structures and the time it takes the orbits to return to the reversal region. Observations in some of the previous literature are discussed. ¿ American Geophysical Union 1994