  The detection of bright X-ray features and large TeV halos around old pulsars
that have escaped their parent Supernova Remnants and are interacting directly
with the ISM, suggest that high energy particles, more likely high energy
pairs, can escape from these systems, and that this escape if far more complex
than a simple diffusive model can predict. Here we present for the first time a
detailed analysis of how high energy particles escape from the head of the bow
shock. In particular we focus our attention on the role of the magnetic field
geometry, and the inclination of the pulsar spin axis with respect to the
direction of the pulsar kick velocity. We show that asymmetries in the escape
pattern of charged particles are common, and they are strongly energy
dependent. More interestingly we show that the flow of particles from bow-shock
pulsar wind nebulae is likely to be charge separated, which might have profound
consequences on the way such flow interacts with the ISM magnetic field,
driving local turbulence.
