Quasi-linear theory of Cherenkov-drift instability: Application for radio pulsars

¹ Institute of Astronomy, University of Zielona Góra, Lubuska 2, 65-265 Zielona Góra, Poland
² Center for Plasma Astrophysics, Abastumani Astrophysical Observatory, Al.Kazbegi ave. 2a, Tbilisi 380060, Georgia

Corresponding author: D. Shapakidze, shapo@ia.uz.zgora.pl

Received: 5 June 2002
Accepted: 4 July 2002

Abstract

We present a plasma model for formation of discontinuous position-angle curves observed in some radio pulsar profiles. The model is based on the polarization properties of radio waves excited by Cherenkov-drift instability developing in pulsar magnetospheres. The radiation is confined in a cone of emission and consists of two orthogonally polarized waves. Examination of a quasi-linear stage of Cherenkov-drift instability shows that the excitation mechanism provides the modes with different spectral energy densities depending on the direction of . As a pulsar rotates, an observer's sight-line track crosses different mode-predominated areas on the base of the emission cone. Transition of the sight-line track from one mode-predominated area to another results in the formation of pulsar polarization fluctuations observed in polarization angle distribution displays and average waveforms.