Pair production near threshold in pulsar magntic fields Available to Purchase

In pulsar polar cap models, curvature radiation γ{‐rays produce e⁺e⁻ pairs in the strong magnetic fields near the surface of the neutron star. While these γ‐rays have energies E_γ≫mc², they also propagate at very small angles to the field, such that the threshold condition, E_γ≳2mc²/sinθ is just barely satisfied when they pair produce. Threshold effect on the pair production attenuation coefficient, which are due to the discreteness of the e⁺e⁻ Landau states, must therefore be considered when computing the mean free paths of curvature radiation photons in pulsar magnetic fields. These effects, which are not incorporated in the asymptotic expression for the attenuation coefficient, have some interesting consequences for pulsar models. Since pair production is suppressed near threshold, the photon mean free paths are longer than previously thought. In magnetic fields ≳6×10¹² G, the pairs tend to be produced in the ground state Landau level and will not synchrotron radiate. Since synchrotron radiation is an essential ingredient in the electromagnetic cascades which produce low energy pairs above the acceleration region, pulsars with very high magnetic fields may not produce many pairs.