  Zitterbewegung (ZB, the trembling motion) of free relativistic electrons in a
vacuum in the presence of an external magnetic field is calculated. It is shown
that the motion of an electron wave packet has intraband frequency components,
corresponding to the classical cyclotron motion, and several interband
frequency components corresponding to the Zitterbewegung. For a two-dimensional
situation, the presence of a magnetic field makes the ZB motion stationary,
i.e. not decaying in time. We show how to simulate the ZB in a magnetic field
using trapped ions and laser excitations in the spirit of recently observed
proof-of-principle ZB simulation by Gerritsma {\it et al.} Nature {\bf 463}, 68
(2010). It is demonstrated that, for the parameters of the Dirac equation
simulated by the above experiment, the effect of a magnetic field on the
Zitterbewegung is considerable.
