Interaction and ablation of fall-back discs in isolated neutron stars

An analysis of ablation processes is made for a fall-back disc with inner and outer radii external to the neutron-star light cylinder. The calculated ablation rate leads, with certain other assumptions, to a simple expression relating the inner radius and mean mass per unit area of any long-lived fall-back disc. Expressions for the torque components generated by interaction with the pulsar wind are obtained. It is not impossible that these could be responsible for small observable variations in pulse shape and spin-down rate but they are unlikely to be the source of the periodic changes seen in several pulsars.