  The paper reports on the dynamics of a 3-dimensional dusty plasma in a strong
magnetic field. An electrostatic potential well created by a conducting or
non-conducting ring in the rf discharge confines the charged dust particles. In
the absence of the magnetic field, dust grains exhibit a thermal motion about
their equilibrium position. As the magnetic field crosses a threshold value (B
$>$ 0.02 T), the edge particles start to rotate and form a vortex in the
vertical plane. At the same time, the central region particles either exhibit
thermal motion or $\vec{E} \times \vec{B}$ motion in the horizontal plane. At B
$>$ 0.15 T, the central region dust grains start to rotate in the opposite
direction resulting in a pair of counter-rotating vortices in the vertical
plane. The characteristics of the vortex pair change with increasing the
strength of the magnetic field (B $\sim$ 0.8 T). At B $>$ 0.8 T, dust grains
exhibit very complex motion in the rotating torus. The angular frequency
variation of rotating particles indicates a differential or sheared dust
rotation in a vortex. The angular frequency increases with increasing the
magnetic field from 0.05 T to 0.8 T. The ion drag force and dust charge
gradient along with the E-field are considered as possible energy sources for
driving the edge vortex flow and central region vortex motion, respectively.
The directions of rotation also confirm the different energy sources
responsible for the vortex motion.
