Properties of frequency distribution of Pc5-range pulsations observed with the Ekaterinburg decameter radar in the nightside ionosphere

Abstract A statistical study of waves in the magnetosphere registered with the midlatitude coherent decameter radar located near Ekaterinburg (EKB), Russia is presented. The radar monitors ionospheric flow velocities whose small-scale variations are evoked by magnetosphere ultra low frequency (ULF) waves of Pc5-range. Data from 16 events observed during 7 months in 2014 and 2015 underwent wavelet analysis. Frequencies of the oscillating components were compared with Alfven eigenfrequencies, which were inferred from THEMIS and Van Allen spacecraft data. The comparison showed that only a minor part of the oscillations registered with the radar in the nightside ionosphere could be attributed to the Alfven mode. A majority of the waves have lower frequencies, which do not show dependence on Alfven eigenfrequency of a field line.