Pulsar extinction

Radio emission from pulsars is attributed to an instability associated with the creation of electron-positron pairs from γ-rays. The condition for pair creation therefore leads to an ''extinction'' condition. The relevant physical processes are analyzed in the context of the ''PCFB'' model, according to which radiation originates at the polar caps and magnetic field lines change from a closed configuration to an open configuration at the ''force-balance'' or ''corotation'' radius.It is found that almost all pulsars with S-type (simple) pulses are in the ''RL'' regime, in which acceleration is radiation-limited. All pulsars with C-type (complex) and D-type (drifting subpulse) pulses are in the complementary ''NRL'' regime. These pulsars are also close to the extinction condition for a pure dipole model, and some pulsars are beyond this condition. In analyzing this model, one may assign a minimum mass to each pulsar in order that the pair-creation condition should be satisfied. This leads, in turn, to a estimate of the minimum surface magnetic field strength for each pulsar. This value is typically in the range 110-1011 gauss and has a maximum value of 1011.4 gauss for the pulsar PSR 2319+60.Calculations are pursed also for the case of a distorted dipole. Pulsars which should be extinguished according to the pure-dipole model need not be extinguished if the magnetic field is sufficiently distorted at the polar caps. The required distortion seems reasonable, except perhaps for the pulsar PSR 1952+29 for which the required radius of curvature of the magnetic-field lines is comparable with the radius of the polar cap