Particle precipitation from the magnetotail during substorms

<正> The dynamics of particles in the magnetosphere during a substorm has been studied. The electromagnetic field of the magnetotail is assumed to be a dawn-dusk electric field and a two-dimensional neutral sheet magnetic field with Bz, where Bz varies with the distance from the earth. The numerical trajectories of the particles show that there is a non-adiabatic region near the equatorial plane, which is determined by δ = |(ρ·(?))B| /B>0.1 (ρ is the Larmor radius). The vanishing of the invariant μ leads to a pitch angle scattering. After a long time of scattering, most of the pitch angles of the particles become small enough for the particles to precipitate into the ionosphere. With the Tsyganenko model, the magnetosphere might be divided into 6 regions: the closed adiabatic region, the open adiabatic region, the non-adiabatic region near the equatorial plane of the near magnetotail, the non-adiabatic region in the cusp, the neutral sheet adiabatic region and the precipitation region. The precipitation