Plasma fluctuations at the flanks of the Earth's magnetosheath at ion kinetic scales

Abstract. We present a statistical study of the magnetosheath plasma fluctuation spectra at a high-frequency range (with frequencies from 0.01 to 10 Hz). Variations of ion flux value and its direction are considered. The direction of ion flux is characterized by a polar angle – the deviation of the ion flux vector from the Sun–Earth line. We consider 290 Fourier's spectra that can be described by two power laws with a break, i.e., a change of slope. The ion flux fluctuation spectra are shown to have breaks at higher frequencies compared to the polar angle spectra. We compare the frequency of the break with the gyrostructure frequency for a number of cases. We show the polar angle break frequency to usually be smaller than the gyrostructure frequency. The dependencies of spectrum parameters such as the slopes and the break frequency on plasma parameters are also considered.