Rotation Powered Pulsars as Sources of High-Energy Particles

Abstract

Highly magnetised rapidly spinning neutron stars are widely considered to be natural sites for acceleration of charged particles. A powerful acceleration mechanism due to unipolar induction is thought to operate in the magnetospheres of isolated neutron stars, bringing the particles to ultrarelativistic energies at the expense of the neutron star rotational energy, with inevitable emission of high energy photons. The aim of this review is to present the basic ingredients of modern models of magnetospheric activity of rotation powered pulsars in the context of high-energy radiation from these objects. Several aspects of pulsar activity are addressed and related to spectacular results of pulsar observations with two major satellite missions of the past - CGRO and ROSAT. It is then argued that future high sensitivity experiments - GLAST, VERITAS, and MAGIC - will be vital for a progress in our understanding of pulsar magnetospheric processes. In a conservative approach rotation powered pulsars are not expected to be the sources of ultra high energy cosmic rays. However, several scenarios have been proposed recently to explain the ultra high energy cosmic ray events above the Greisen-Zatsepin-Kuzmin limit with the help of acceleration processes in the immediate surrounding of newly born pulsars. Major features of these scenarios are reviewed along with references to contemporary models of magnetospheric activity.