The paper presents the latest results of the studies of small-scale fluctuations in a turbulent flow of solar wind (SW) using measurements with extremely high temporal resolution (up to 0.03 s) of the bright monitor of SW (BMSW) plasma spectrometer operating on astrophysical SPECTR-R spacecraft at distances up to 350 000 km from the Earth. The spectra of SW ion flux fluctuations in the range of scales between 0.03 and 100 s are systematically analysed. The difference of slopes in low- and high-frequency parts of spectra and the frequency of the break point between these two characteristic slopes was analysed for different conditions in the SW. The statistical properties of the SW ion flux fluctuations were thoroughly analysed on scales less than 10 s. A high level of intermittency is demonstrated. The extended self-similarity of SW ion flux turbulent flow is constantly observed. The approximation of non-Gaussian probability distribution function of ion flux fluctuations by the Tsallis statistics shows the non-extensive character of SW fluctuations. Statistical characteristics of ion flux fluctuations are compared with the predictions of a log-Poisson model. The log-Poisson parametrization of the structure function scaling has shown that well-defined filament-like plasma structures are, as a rule, observed in the turbulent SW flows.

The magnetosheath is a natural laboratory for the study of plasma turbulence. The magnetopause and the bow shock prevent freely development of turbulence and modify turbulent cascade. In this...

The Earth’s magnetosphere is permanently influenced by the solar wind. When supersonic and superalfvenic plasma flow interacts with the magnetosphere, the magnetosheath region is formed, which is filled with shocked turbulent plasma. Varying SW parameters influence the mechanisms of formation of this boundary layer, including the dynamics of turbulence behind the bow shock. The effect of the solar wind on the development of turbulence in the magnetosheath was demonstrated recently based on broad statistics of spacecraft measurements. The present study considers the multipoint observations of turbulent fluctuations in the solar wind, in the dayside magnetosheath and at the flanks, to analyze the evolution of the turbulent cascade while the solar wind plasma enters the magnetosheath. Observations of the magnetosheath behind the quasi-perpendicular bow shock are analyzed to exclude the influence of the bow shock topology from consideration. Three basic types of solar wind flows are considered: slow undisturbed solar wind, compressed regions, and interplanetary manifestations of coronal mass ejections. The results show surviving Kolmogorov scaling behind the bow shock for steady solar wind flow and amplification of the compressive fluctuations at the kinetic scales at the magnetosheath flanks for the solar wind associated with compressed plasma streams. During interplanetary manifestations of the coronal mass ejection, the spectra in the dayside magnetosheath substantially deviate from those observed in the solar wind (including the absence of Kolmogorov scaling and steepening at the kinetic scales) and restore at the flanks.

The paper is devoted to the shapes of the solar wind ion flux fluctuation spectrum at the transition between the inertial and the kinetic range usingin situhigh-resolution measurements of the Russian mission Spektr-R. We analyse the variability of the transition region and select five typical types of spectral shapes: (i) spectra with two slopes and one break, (ii) spectra characterized by a nonlinear steepening in the kinetic range, (iii) spectra with flattening in the vicinity of the break, (iv) spectra with a bump in the vicinity of the break and (v) spectra without any steepening in the kinetic range. The most popular is the well-known type (i) observed in approximately half of the cases. The second most popular type of spectra is type (iii) occurring in approximately one third of the cases. The other three types are observed less often: type (ii) – in approximately 6 %; type (iv) in 3 % and type (v) in 6 % of cases. An analysis of typical plasma conditions for different types of spectra revealed that the last two type of spectra (iv) and (v) are generally observed in a very slow solar wind with a low proton density, (i) and (iii) are observed in the solar wind with rather typical conditions and (ii) is usually observed in high-speed streams. The effect of nonlinear steepening of the spectra in the kinetic range increases with the solar wind speed. We present also the analysis of statistical properties of the observed events and compare them with the predictions of several statistical turbulence models. We show that intermittency is always observed in the solar wind flow despite the presence of one or another shape of spectra. The log-Poisson model with a dominant contribution of filament-like structures shows the best parameterization of the experimentally observed scaling.

In solar cycles 23–24, solar activity noticeably decreased and, as a result, solar wind parameters decreased. Based on the measurements of the OMNI base for the period 1976–2019, the time profiles of the main solar wind parameters and magnetospheric indices for the main interplanetary drivers of magnetospheric disturbances (solar wind types CIR. Sheath, ejecta and MC) are studied using the double superposed epoch method. The main task of the research is to compare time profiles for the epoch of high solar activity at 21–22 SC and the epoch of low activity at 23–24 SC. The following results were obtained. (1) The analysis did not show a statistically significant change in driver durations during the epoch of minimum. (2) The time profiles of all parameters for all types of SW in the epoch of low activity have the same shape as in the epoch of high activity, but locate at lower values of the parameters. (3) In CIR events, the longitude angle of the solar wind flow has a characteristic S shape; but in the epoch of low activity, it varies in a larger range than in the previous epoch.

The turbulent characteristics of plasma fluctuations in the solar wind (SW) may substantially change depending on the SW conditions. Large-scale streams of different types, such as...