  The spontaneous rotation of small dust clusters confined inside a cubical
glass box in the sheath of a complex plasma was observed in experiment. Due to
strong coupling between the dust particles, these clusters behave like a
rigid-body where cluster rotation is contingent upon their configuration and
symmetry. By evaluating the effects of distinct contributing forces, it is
postulated that the rotation observed is driven by the net torque exerted on
the cluster by the ion wake force. The configuration and symmetry of a cluster
determines whether the net torque induced by the ion wake force is nonzero, in
turn leading to cluster rotation. A COPTIC (Cartesian mesh, oblique boundary,
particles and thermals in cell) simulation is employed to obtain the ion wake
potential providing a theoretical model of cluster rotation which includes both
the ion wake force and neutral drag and predicts rotation rates and direction
in agreement with experimental results. These results are then used to diagnose
the ion flow within the box.
