Physics of auroral phenomena : proceedings of the 40th annual seminar, Apatity, 13-17 March, 2017 / [ed. board: N. V. Semenova, A. G. Yahnin]. - Апатиты : Издательство Кольского научного центра РАН, 2017. - 143 с. : ил., табл.

Properties o fthe magnetosheath plasma turbulence upstream and downstream interplanetary shocks MSH (Spectr-Rji *SW(Thamii-C)! ugstreami downstream; 19 -D ec- 2015 , UT F. Hz Figure 1. Interplanetary shock registered in the Figure 2. Fourier spectra calculated on 17-min magnetosheath by Spektr-R spacecraft on December 19, intervals upstream (black line) and downstream (grey 2015. Black line presents Spectr-R measurements in the line) the interplanetary shock on December 19, 2015. magnetosheath, grey line presents Themis-C Spectral indices are shown in the figure, measurements in the solar wind shifted to match the shock fronts. Intervals used for spectra calculations are shaded. Kolmogorov's predictions of -5/3 ( Kolmogorov, 1941) both downstream and upstream the IP shock. We do not consider this slope further for we deal with kinetic scale turbulence. Spectral slope S 2 is nearly the same upstream and downstream the shock front and is close to -2.6. The break frequency F break increases from 0.75 Hz upstream to 2.07 Hz downstream the front. Such increase can be due to the changes of plasma and magnetic field parameters at the front, that is, characteristic frequencies which are supposed to be responsible for the break position are different upstream and downstream the front. As it was mentioned above, in the solar wind Pitna et al., (2016) showed exponential cutoff of the spectrum downstream the shock front in -50% of cases. The spectrum at Fig. 2 does not exhibit exponential cutoff. We have managed to collect four cases o f IP shock registration in the magnetosheath by Spektr-R spacecraft. All of the cases are observed behind the quasi-perpendicular bow shock. However, two of them are accompanied' by the bow shock crossing in several minutes after IP shock registration. For this reason we cannot calculate reliably spectral indices Si and F break for the lack of data points number. However, the slope S 2 can be calculated. For this reason in the further study we deal only with slope S 2 and power spectral density (PSD) of the spectra. The characteristic o f the shocks and spectra parameters for all of the cases are shown in Table 1. Bolded rows in the table present cases when 17 min time intervals are available upstream as well as downstream the IP shock. In other cases 4 min time intervals are used. Table 1. IP shock registration date IP shock characteristics Spectral slope S 2 p SJ)downstream/ PSDupstream Speed, km/s 0BN^j 0 upstream downstream 15-Mar-2013 460 64 -1.9 -2.0 20 19-Dec-2015 525 55 -2.5 -2.4 40 08-0ct-2013 475 54 -2.2 -2.8 60 27-Feb-2014 375 81 -3.2 -2.0 250 Comparing rows in Table 1 one can conclude that: 1) all of the IP shocks are quasi-perpendicular - 0 bnip >45°; 2) in two cases of four spectral slope S 2 does not change across the shock front, while in other cases both steepening and flattening o f the spectra occur downstream the shock front; 3) for three cases PSD increases by the order of amplitude downstream the IP shock, while in one case (February 27, 2014) it increases by a factor o f 250. In this case the 0вмп> angle is the largest and the shock speed is the smallest comparing to other cases. Turbulence in the space plasma is known to be intermittent (Bruno and Carbone, 2013). Intermittency results in deviation of the probability distribution function (PDF) from the Gauss distribution with decreasing o f scale. Intermittency level can be estimated by the deviation of flatness coefficient - 4-th order moment of the PDF - from the flatness coefficient o f the Gauss PDF - 3 (Frisch , 1995). 83