LAUSR

The influence of a dawn–dusk electric field Ey on transient particles in a 1D current sheet (CS), characterized by the normal (Bz) and tangential (Bx) components of the magnetic field, is studied. The motion and energization of particles injected at the edges of a CS are investigated within the framework of the trajectory method. The analytical treatment reveals that in the case of uniform Bz and Ey, the dynamics of transient particles are described by magnetic flux conservation on specific segments of the trajectory, which allows prediction of some specific properties of the velocity space inside the CS. Verification of the analytical treatment by means of test-particle numerical modeling demonstrates good agreement. In particular, it is shown that the CS can play the role of a converging lens that focuses particles to pitch-angle values close to θ∼π. At the same time, the analysis reveals that the particle energy gain stays within the range of ΔW∈2m[(Ey/Bz)2,(Ey/Bz)(v0+Ey/Bz)], where m is the particle mass and v0 is the initial particle speed (i.e., v0=v·v). The limits of the range depend only weakly on the CS half-thickness. The analysis reveals that for the typical parameters of Ey and Bz in the stationary terrestrial magnetotail, protons with v0≃450 km/s (before CS crossing) can be accelerated along the CS up to vx≃1800 km/s.