  When particles are magnetized, a diffusion process is influenced by the
ambient magnetic field. While the entropy increases, the constancy of the
magnetic moment puts a constraint. Here, we compare the E-cross-B diffusion
caused by random fluctuations of the electric field in two different systems,
the Penning-Malmberg trap and the magnetic dipole trap. A Fokker-Planck
equation is derived by applying the ergodic ansatz on the invariant measure of
the system. In the dipole magnetic field particles diffuse inward and
accumulate in the higher magnetic field region, while, in a homogeneous
magnetic field, particles diffuse out from the confinement region. The
properties of analogous transport in a more general class of magnetic fields
are also briefly discussed.
