The previously proposed concept of ''differential memory'' is quantitatively demonstrated using an idealized analytical model of particle dynamics in the magnetotail geometry. In this model (the ''trilinear'' tail model), the magnetotail is divided into three regions. The particle orbits are solved exactly in each region, thus reducing the orbit integration to an analytical mapping. It is shown that the trilinear model reproduces the essential phase space features of the earlier model (Chen and Palmadesso, 1986), possessing well-defined entry and exit regions, and stochastic, integrable (regular), and transient orbits, occupying disjoint phase space regions. Different regions have widely separated characteristic time scales corresponding to different types of particle motion. Using the analytical model, the evolution of single-particle distribution functions is calculated. ¿ American Geophysical Union 1990