Current flow in pulsar magnetospheres

When particle flow is mainly outward through the light cylinder of a rotating pulsar magnetosphere, the resulting current flow leads to very large potential drops along field lines wherever the product of the angular velocity and the magnetic-field intensity vanishes. These occur no matter what the sign of the charge above the magnetic polar cap. For fast pulsars, such a gap potential drop is limited by pair-production discharge. In such models, current flow into and out of the pulsar polar cap is always carried by particles of the same sign unless the magnetic polar axis is nearly perpendicular to the spin axis. For the Crab pulsar, the gap potential at breakdown is about 10 to the 14th power V, and the resulting radiation is mainly hard X-rays and gamma-rays up to 100 GeV. The latter are expected to be emitted almost perpendicular to the magnetic axis and probably, therefore, should be observed almost 90 deg earlier in phase than much lower-energy pulsar emission.