  Active particles with a (magnetic) dipole moment are of interest for steering
self-propelled motion, but also result in novel collective effects due to their
dipole-dipole interaction. Here systems of active dipolar particles are studied
with Brownian dynamics simulations to systematically characterize the different
patterns they form, specifically in the presence of an external (magnetic)
field. The combination of three types of order - clustering, orientational
alignment and chain formation - is used to classify the patterns observed in
these systems. In the presence of an external field, oriented chains and bands
are found to be dominant. These structures show some similarities with columnar
cluster seen in (passive) ferrofluids and display columnar spacing and number
of lanes per cluster that both decrease with increasing field strength.
