  In this paper we analyze the dynamical behavior of large dust grains in the
vicinity of a cometary nucleus. To this end we consider the gravitational field
of the irregularly shaped body, as well as its electric and magnetic fields.
Without considering the effect of gas friction and solar radiation, we find
that there exist grains which are static relative to the cometary nucleus; the
positions of these grains are the stable equibria. There also exist grains in
the stable periodic orbits close to the cometary nucleus. The grains in the
stable equibria or the stable periodic orbits will not escape or impact on the
surface of the cometary nucleus. The results are applicable for large charge
dusts with small area-mass ratio which are near the cometary nucleus and far
from the Solar. It is found that the resonant periodic orbit can be stable, and
there exist stable non-resonant periodic orbits, stable resonant periodic
orbits and unstable resonant periodic orbits in the potential field of cometary
nuclei. The comet gravity force, solar gravity force, electric froce, magnetic
force, solar radiation pressure, as well as the gas drag force are all
considered to analyze the order of magnitude of these forces acting on the
grains with different parameters. Let the distance of the dust grain relative
to the mass centre of the cometary nucleus, the charge and the mass of the dust
grain vary, respectively, fix other parameters, we clacluated the strengths of
different forces.
