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

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 $\vec{k}$. 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

Dynamical feedback of the curvature drift instability on its saturation process

Aims. We investigate the reconstruction of pulsar magnetospheres close to the light cylinder surface to study the curvature drift instability (CDI) responsible for the twisting of magnetic field lines in the mentioned zone. The influence of plasma dynamics on the saturation process of the CDI is studied. Methods. On the basis of the Euler, continuity, and induction equations, we derive the increment of the CDI and analyze parametrically excited drift modes. The dynamics of the reconstruction of the pulsar magnetosphere is studied analytically. Results. We show that there is a possibility of a parametrically excited rotational-energy pumping-process in the drift modes. It is indicated by the generation of a toroidal component of the magnetic field that transforms the field lines into such a configuration, in which plasma particles do not experience any forces. At this stage, the instability process saturates and the further amplification of the toroidal component to the magnetic field lines is suspended