The Partially Screened Gap (PSG) in pulsar magnetosphere: Theory and Observations

George I. Melikidze
University of Zielona Gora

Rotation Powered Pulsars have an active magnetosphere where pair plasma can accelerate in localized regions of high electric fields, the so called gap regions. To explain observational features of coherent radio and x-ray emission from pulsar, the ``gap'' needs to form above the polar cap surface and the electric field in the gap should be partially screened. The model of the partially screened polar gap (PSG) assumes that the magnetic field at the stellar surface is very strong and differs essentially from the pure dipolar magnetic field structure. This assumption is well supported by calculations of the cohesive energy for the neutron star surface, which show that the accelerating gap above polar cap can form provided that the local surface magnetic field is about 10^{^14} G. In addition, X-ray observations of radio pulsars make it clear that the hot spot surface is much smaller than that of the canonical one obtained from the dipolar geometry. The high curvature of the field lines, which is an essential condition for creation of dense electron-positron plasma necessary for the radio emission generation depends on the ratio of the dipolar and crust anchored fields.