THEORY OF THE MOTION OF A RELATIVISTIC CHARGED PARTICLE IN HIGHLY NONUNIFORM CROSSED ELECTRIC AND MAGNETIC FIELDS.

The asymptotic Krylov-Bogolyubov method is used to study the motion of a relativistic charged particle in crossed fields. In contrast to the well-known adiabatic theory of charged particle motion the electric field is not assumed weak, and the magnetic field is not assumed slowly varying. It is shown that in the case under consideration there exists an adiabatic invariant differing from the invariant in the conventional theory. The interaction of a relativistic charged particle with the front of a collisionless MHD shock wave of finite thickness is studied with the resulting evolution equations and the new adiabatic invariant.