2002A&A...385..671F

Two events demonstrating periodic narrowband millisecond pulsations of radio emission both in intensity and polarization degree are analyzed. Large time delays between L- and R-polarization components are found. The radio emission is shown to be generated as unpolarized by a plasma mechanism at the second harmonic of the upper-hybrid frequency. Observed oscillations of the radiation polarization degree arise due to group delay between extraordinary and ordinary modes along the line of sight. The theoretically predicted dependence of the group delay on frequency (∼f^–3) agrees excellently with the observed delay frequency dependence. Physical parameters of the emission source and ``delay site'' are determined within the proposed model.