Modeling of pitch angle distribution on the dayside of the Earth's magnetosphere

The mathematical model of pitch-angle diffusion in the magnetosphere which allows to compute theoretically density of phase space or pitch angle distribution of the charged particles is offered. On concrete examples of pitch angle distribution evolution during the 1–7 May 1998 geomagnetic storm within its last 68 hours potential opportunities of offered model of pitch-angle diffusion on the dayside of the Earth's magnetosphere are shown.