Complex demodulation applied to Pi2 geomagnetic pulsations

The spectral technique of complex demodulation is applied to Pi2 pulsations recorded along a meridional profile. The technique provides instantaneous values of amplitude and phase and allows frequency dispersion to be taken into account. The variations of magnetospheric wave polarization parameters are observed as a function of both space and time. The results are directly compared with recent theories of the resonance of geomagnetic field lines and the effects of the ionosphere on ground based observations. The theoretical predictions are tested and the experimental results indicate that the night-time ionosphere is capable of a controlling influence on the source characteristics of these magnetospheric waves in the plasmapause region.