  In this paper we study relativistic dynamics of charged particles co-rotating
with prescribed trajectories, having the shape of dipolar magnetic field lines.
In particular, we consider the role of the drag force caused by the photon
field the forming of equilibrium positions of the charged particles. Alongside
a single particle approach we also study behaviour of ensemble of particles in
the context of stable positions. As we have shown, together they create
surfaces where particles are at stable equilibrium positions. In this paper we
examine these shapes and study parameters they depend on. It has been found
that under certain conditions there are two distinct surfaces with stable
equilibrium positions.
