ABSTRACT
This chapter discusses the motion of individual charged particles in slowly varying electric and magnetic fields. In general, the fields in the magnetosphere change on a length scale which is long compared with the gyroradius and a time scale long compared with the gyroperiod. A transverse magnetic field gradient exerts a force on a magnetic dipole aligned with the field. Also the path of the guiding centre is curved due to the curvature of the fields and their rate of change with time. In a uniform magnetic field, the integral of the magnetic force over one complete cyclotron orbit is zero. If the magnetic field has a transverse gradient, the magnetic force varies from point to point along the orbit of the particle and the force does not average to zero over the orbit. The chapter discusses the particle drifts and bounces steadily round the earth with uniform drift and bounce frequencies.
