Polarization Characteristics of High-Latitude Pi3 Geomagnetic Pulsations

The results of a statistical study of the polarization characteristics of irregular geomagnetic Pi3 pulsations observed in polar regions of the magnetosphere and the effect of interplanetary conditions on them are presented. One-minute digital observations of the magnetic field of the Heiss Island (HIS, phi' = 74.80 degrees, ?' = 144.46 degrees) and Mirny (MIR, phi' = -76.93 degrees, ?' = 122.92 degrees) observatories are used. Pi3 pulsations are characterized by right-handed, left-handed, and mixed polarizations (R, L, and R&L types, respectively). Regardless of the polarization type, Pi3 pulsations have been observed mainly in the night sector of the magnetosphere at the final stage of the explosive phase of the substorm. The duration of the time delay between the substorm onset and the occurrence of Pi3 pulsations depends significantly on their polarization type. HIS and MIR show no dependence of the main characteristics (amplitude, frequency, ellipticity, and tilt of the main axis of the polarization ellipse) of Pi3 pulsations of R, L, and R&L types on local time. In HIS, R- and R&L-type Pi3 pulsations are observed mainly during slow solar-wind streams, and L-type pulsations are observed during high-speed streams from coronal holes. In MIR, Pi3 pulsations of the three polarization types are observed mainly during high-speed solar-wind streams. Small-scale closed structures of the magnetic field in the flow of slow and fast solar-wind currents determine the polarization type of Pi3 pulsations. It is revealed that the excitation of Pi3 pulsations of the R, L, and R&L types occurs at different levels of plasma turbulence in the magnetotail.