  Bow Shock Pulsar Wind Nebulae are a class of non-thermal sources, that form
when the wind of a pulsar moving at supersonic speed interacts with the ambient
medium, either the ISM or in a few cases the cold ejecta of the parent
supernova. These systems have attracted attention in recent years, because they
allow us to investigate the properties of the pulsar wind in a different
environment from that of canonical Pulsar Wind Nebulae in Supernova Remnants.
However, due to the complexity of the interaction, a full-fledged
multidimensional analysis is still laking. We present here a simplified
approach, based on Lagrangian tracers, to model the magnetic field structure in
these systems, and use it to compute the magnetic field geometry, for various
configurations in terms of relative orientation of the magnetic axis, pulsar
speed and observer direction. Based on our solutions we have computed a set of
radio emission maps, including polarization, to investigate the variety of
possible appearances, and how the observed emission pattern can be used to
constrain the orientation of the system, and the possible presence of
turbulence.
