On the origin of giant pulses in radio pulsars

Institute of Radio Astronomy, 4, Chervonopraporna St., Kharkov, 61002 Ukraine e-mail: rai@ira.kharkov.ua

Received: 30 January 2004
Accepted: 11 May 2004

Abstract

Induced Compton scattering of radio emission off the particles of the ultrarelativistic highly magnetized plasma of pulsar magnetosphere is considered. The scattering between the photon beams of substantially differing frequencies and orientations appears to result in photon transfer to the higher frequency. With the decreasing spectrum of pulsar radio emission, this may imply a significant amplification of the higher-frequency intensity. A detailed analysis shows that the rays of widely spaced frequencies can have different orientations, at least at certain locations in the pulsar magnetosphere. The numerical estimates confirm the possibility of an efficient beam-to-beam scattering in the pulsars known as giant pulse sources. Thus, the intensity amplification on account of induced scattering of the lower-frequency radiation is suggested to underlie the giant pulse phenomenon. A huge pulse-to-pulse scatter in the observed intensities of the giant pulse sources (over more than three orders of magnitude) testifies to significant variations of the efficiency of amplification. If this variability is attributed to the fluctuations of both the particle number density and the incident intensity and the latter are considered as the partially correlated Gaussian random quantities, one arrives at the power-law distribution of strong pulses in intensity. The formation of the giant pulse substructure, the broad-band spectral behaviour of the scattering efficiency and the link of giant pulses to the high-energy emission are discussed as well.