Resonant Inverse Compton Scattering above Polar Caps: Gap Acceleration Efficiency for Young Pulsars

It is shown that for moderately hot polar caps (with effective temperature of ∼10⁶ K), the efficiency of polar gap acceleration is lower compared to the case in which the polar caps are relatively cool and inverse Compton scattering plays no role in controlling the gap. For young pulsars with superstrong magnetic fields (≥10⁹ T) and hot polar caps (with temperature of ≥5 × 10⁶ K), because of the energy loss of electrons or positrons due to resonant inverse Compton scattering in the vicinity of polar caps, pair cascades occur at distances further away from the polar cap, and in this case we have a relatively high acceleration efficiency, with ions carrying most of the particle luminosity.