The trajectories of mirroring protons and electrons are obtained by tracing in a realistic model of the magnetosphere. We found day-night asymmetry in the particle trajectories, which is caused by the asymmmetry in gradient and curvature drifts. Also, we found that the high-energy protons injected from the nightside escape from the duskside magnetopause. This may be important for the explanation of partial ring current closure. ¿ American Geophysical Union 1989