Kinetic-Scale Ion Flux Fluctuations Behind the Quasi-Parallel and Quasi-Perpendicular Bow shock

Properties of kinetic-scale plasma turbulence are examined observationally with the help of Spektr-R measurements in the Earth's magnetosheath. The statistics covers 6 years of ion flux measurements during years 2011-2017 and includes a few dozens of the magnetosheath crossings with total duration of 250 hr. Several types of Fourier spectra are distinguished in the magnetosheath according to a spectral shape at the scales of transition from magnetohydrodynamic to kinetic regimes. Spectral indices and occurrence rate of different spectral shapes are examined at different locations with respect to the magnetosheath boundaries-the magnetopause and the bow shock. Magnetosheath plasma behind the quasi-parallel and quasi-perpendicular bow shock is explored separately. Clear dynamics of spectral shapes across the magnetosheath is shown: spectra with broad bump at the transition frequencies occur more frequently in the vicinity of the bow shock, while spectra with plateau at the same frequencies are usually observed closer to the magnetopause. Spectral indices such as spectral slope at the kinetic scales and break frequency are shown to be weakly affected by the boundaries behind the quasi-perpendicular bow shock. The steepest spectra are observed close to the quasi-parallel bow shock.