Pulsar magnetospheres and emission mechanisms

It is shown that an electron-positron pair plasma will generally be created above a positively charged polar cap, in various models for ion flow out of the neutron star surface and for various pair production discharge mechanisms. A potential drop may arise above a pulsar polar cap either from the inertia of freely released ions in a space charge limited flow, or from surface binding of ions leading to charge depletion and gap formation. Pair production discharges which limit this potential drop may arise from Sturrock-Goldreich discharges with pair creation in the stellar magnetic field, or pair production by thermal x-rays from the polar cap surface in the Coulomb field of relativistic ions or electrons and positrons accelerated through the discharge region. In all cases the properties of the resulting electron-positron pair plasma are similar, except that the number density may be less when the ion flow is space charge limited