Pair production in the millisecond pulsar J0030+0451

Abstract

The electric field accelerating electrons in the Timokhin-Arons polar-cap model as applied to millisecond pulsars is so high that the electron Lorentz factors are limited either by radiation reaction or by the Breit-Wheeler process. In the former case, it is possible to obtain an upper limit for curvature radiation momentum components perpendicular to the local magnetic field which is independent of the flux-line radius of curvature. The threshold value for single-photon conversion to pairs is high but is possibly reached in J0030+0451. However, owing to the high polar-cap temperature reported, direct pair production by the Breit-Wheeler process is probably more important. If the existence of coherent radio emission in millisecond pulsars is assumed to need a high-multiplicity pair plasma, then it follows that the primary electrons also produce gamma-rays in the Fermi-LAT energy band for which the magnetosphere is completely transparent. The absence of these, in phase with the radio emission, would be an immediate indication that ultra-high energy electrons and an active Timokhin-Arons polar cap are not present in J0030+0451.