Wave effects of sudden impulse and substorm onset in the magnetosphere morning sector on 4 January 2001

A comparative analysis of ULF-waves registered after sudden impulse (SI) and the following substorm onset (SO) by the Cluster satellites at distances L~4 from the Earth's centre was made. It was shown that both phenomena mentioned above activated magnetic field oscillations of periods from 40 to 200 s. Oscillations followed SI and SO were found to be of a similar spectral composition but different polarizations. Differences in polarization became well-pronounced in a range of the main spectral maximum (100-130 s) where the transition from SI to SO was accompanied by change in direction of rotation of magnetic field disturbance vector and by reorientation of oscillation polarization ellipse.