  The effective potential energy of the particles in the field of rotating
uniformly magnetized celestial body is investigated. The axis of rotation
coincides with the axis of the magnetic field. Electromagnetic field of the
body is composed of a dipole magnetic and quadrupole electric fields. The
geometry of the trapping regions is studied as a function of the magnetic field
magnitude and the rotation speed of the body. Examples of the potential energy
topology for different values of these parameters are given. The main
difference from the classical St{\o}rmer problem is that the single toroidal
trapping region predicted by St{\o}rmer is divided into equatorial and
off-equatorial trapping regions. Applicability of the idealized model of a
rotating uniformly magnetized sphere with a vacuum magnetosphere to real
celestial bodies is discussed.
