  The structure of a finite particle cluster is typically determined by total
energy minimization. Here we consider the case where a cluster of soft sphere
dipoles becomes active, i.e. when the individual particles exhibit an
additional self-propulsion along their dipole moments. We numerically solve the
overdamped equations of motion for soft-sphere dipoles in a solvent. Starting
from an initial metastable dipolar cluster, the self-propulsion generates a
complex cluster dynamics. The final cluster state has in general a structure
widely different to the initial one, the details depend on the model parameters
and on the protocol of how the self-propulsion is turned on. The center-of-mass
of the cluster moves on a helical path, the details of which are governed by
the initial cluster magnetization. An instantaneous switch to a high
self-propulsion leads to fission of the cluster. However, fission does not
occur if the self-propulsion is increased slowly to high strengths. Our
predictions can be verified through experiments with self-phoretic colloidal
Janus-particles and for macroscopic self-propelled dipoles in a highly viscous
solvent.
