On the role of the current loss mechanism in radio pulsar evolution

Abstract

The aim of this article is to draw attention to the importance of the electric current loss in the energy output of radio pulsars. We remind that even the losses attributed to the magneto-dipole radiation of a pulsar in vacuum can be written as a result of Ampere force action of the electric currents flowing over the neutron star surface (Michel 1991, Beskin, Gurevich & Istomin 1993). It is this force that is responsible for the transfer of angular momentum of a neutron star to an outgoing magneto-dipole wave. If a pulsar is surrounded by plasma, and there is no longitudinal current in its magnetosphere, there is no energy loss (Beskin, Gurevich & Istomin 1993, Mestel, Panagi & Shibata 1999). It is the longitudinal current closing within the pulsar polar cap that exerts the retardation torque acting on the neutron star. This torque can be determined if the structure of longitudinal current is known. Here we remind of the solution by Beskin, Gurevich & Istomin (1993) and discuss the validity of such an assumption. Finally, it is shown that the behaviour of the recently observed "part-time job" pulsar B1931+24 can be naturally explained within the model of current loss while the magneto-dipole model faces difficulties.