We have analyzed spectra of fluctuations in the solar wind plasma flux and the magnetic field magnitude near the front of a fast reverse shocks, using data from the BMSW device (Bright Monitor of Solar Wind) operating on the SPEKTR-R satellite. Its time resolution made it possible to study plasma flux fluctuations up to a frequency of 16 Hz. Magnetic field data was taken mainly from the WIND satellite, for which the frequency of the fluctuations considered was up to 5.5 Hz. The slope of the spectra of the solar wind flux fluctuations on MHD scales has been shown to be close to the slope of the spectrum of magnetic field fluctuations in the disturbed region. On kinetic scales, the difference can be significant. For the region ahead of the front, the difference in the slope of the spectrum can be quite large both in the MHD and in the kinetic region. The frequency of the break of the flux spectrum ranges from 0.6 to 1.3 Hz, which corresponds to the scale of the proton inertial length. In a number of events, however, the shape of the spectrum indicates the influence of the proton gyroradius frequency, which is usually 0.05–0.15 Hz. The break in the power spectrum of magnetic field fluctuations also more often ranges from 0.7 to 1.2 Hz. In this case, the slope of the MHD part of the spectrum changes little, but in the kinetic part it increases slightly when moving to the disturbed region.

The paper investigates the characteristics of the power spectra of fluctuations in the density of protons and α particles near the front of the interplanetary (IP) and Earth’s bow shock (BS). The frequencies of the power spectra break of fluctuations in the density of protons and α particles were calculated before and behind the ramp of the Earth’s bow shock and interplanetary shock. For the disturbed solar wind beyond the IP ramp, the frequency of the spectrum break of proton fluctuations turned out to be noticeably higher (on average 1.3 Hz) than in the undisturbed region (∼0.8–1.0 Hz), which is explained by an increase in both the velocity and the density of particles. In the case of α particles, the frequency of the spectrum break of fluctuations behind the IP front also increased by almost two times (from 0.7 to 0.12 Hz). It is shown that the average value of the frequency of the proton spectra break behind the ramps is less (0.6 Hz) than in the solar wind (1.0 Hz), due to lower velocity. For α particles, this effect was not statistically detected due to an increase in the density (0.11 Hz for both regions) in the case of BS.

Wave trains of magnetic field and ion-flux oscillations generated upstream of the ramp of interplanetary (IP) shock were studied according to BMSW plasma-spectrometer measurements of energy–time spectra of the solar-wind ions supplemented by magnetic-field measurements. It was shown that oscillations of the magnetic field upstream of the ramp of IP shock are accompanied by oscillations of the ion flux. A detailed analysis of two cases is carried out, and the results of statistical study are presented. Right-handed circular or elliptical polarization was observed in all wave trains of magnetic-field oscillations, which is consistent with the characteristics of magnetosonic oscillations corresponding to the low-frequency branch of whistler waves. It was obtained that the mean angles between the propagation direction of whistler waves relative to the magnetic field and shock normal direction were 31° and 40°, respectively. This result suggests that the wave packets upstream of the ramp of IP shock had the properties of propagating whistler waves. It was found that, on average, with an increase in the angle of propagation of whistler waved relative to the shock normal direction θkn, the angle between the wave vector and magnetic-field direction θkB decreases.

Исследуются характеристики спектров мощности флуктуаций плотности протонов и альфа-частиц вблизи фронта межпланетной и околоземной ударной волны. Были посчитаны частоты излома спектров мощности флуктуаций концентрации протонов и альфа-частиц перед и за рампом околоземной ударной волны (ОЗУВ) и межпланетной ударной волны (МУВ). Для возмущенного солнечного ветра за рампом МУВ частота излома спектра флуктуаций протонов оказалась заметно выше (в среднем 1.3 Гц), чем в невозмущенной области (~0.8–1.0 Гц), что объясняется увеличением как скорости, так и концентрации частиц. В случае альфа-частиц частота излома спектра флуктуаций за фронтом МУВ также повышалась – почти в два раза (от 0.7 до 0.12 Гц). Показано, что среднее значение частоты излома спектров протонов за рампом ОЗУВ меньше (0.6 Гц), чем в солнечном ветре (1.0 Гц), ввиду меньшей скорости. Для альфа-частиц этот эффект статистически не был обнаружен из-за увеличения концентрации (0.11 Гц для обеих областей) в случае ОЗУВ.

In this work, the possibilities of the magnetosheath-magneto-sphere model for describing the plasma parameters in the magnetosheath are demonstrated. We consider the problem of a flow around a body (the Earth's magnetosphere) with two movable boundaries - the bow shock (BS) and the magnetopause (MP). The grid-characteristic method is applied to describe an ideal gas flow in the transition region (magnetosheath). A theoretical finite element model and the semi-empirical Tsyganenko model are used to describe the magnetic field in the magnetosphere. The model allows a self-consistent determination of the magnetosheath boundaries for a given momentary state of the solar wind. For these input parameters the three-dimensional solution in the transition region is calculated. An analysis of the ion flux was made based on the model and the data measured by the Interball-1 satellite in several cases of magnetosheath crossings. The advantages and limitations of the model for describing the magnetosheath flow are analyzed.

Solar activity and solar wind parameters decreased significantly in solar cycles (SCs) 23–24. In this paper, we analyze solar wind measurements at the rising phase of SC 25 and compare them with similar data from the previous cycles. For this purpose, we simultaneously selected the OMNI database data for 1976–2022, both by phases of the 11-year solar cycle and by large-scale solar wind types (in accordance with catalog [http://www.iki.rssi.ru/pub/omni]), and calculated the mean values of the plasma and magnetic field parameters for the selected datasets. The obtained results support the hypothesis that the continuation of this cycle will be similar to that of cycle 24, i.e. SC 25 will be weaker than SCs 21 and 22

Solar activity and solar wind parameters decreased significantly in solar cycles (SCs) 23-24. In this paper, we analyze solar wind measurements at the rising phase of SC 25 and compare them with similar data from the previous cycles. For this purpose, we simultaneously selected the OMNI database data for 1976-2022, both by phases of the 11-year solar cycle and by large-scale solar wind types (in accordance with IKI's catalog, see http://www.iki.rssi.ru/pub/omni ), and calculated the mean values of the parameters for the selected datasets. The obtained results testify in favor of the hypothesis that the continuation of this cycle will be similar to the previous cycle 24, i.e. SC 25 will be weaker than SCs 21 and 22.

This article investigates variations in the parameters of the twice ionized helium ions He++ (α-particles) of the solar wind plasma when crossing shock fronts in collisionless plasma, that is, interplanetary (IP) shocks and the Earth’s bow shock. Data from measurements of the BMSW instrument mounted on the SPEKTR-R satellite are used. Using data from this instrument, the parameters of protons and α-particles in the solar wind (velocity, temperature, density, magnitude and direction of the flux, and the relative density of He++ ions) are calculated. It is shown that the absolute density of He++ ions increases behind the shock front (of both the IP and the bow shock), while the relative density of He++ ions decreases behind the IP front and increases behind the bow shock front. A correlation between the change in the relative density of He++ ions and the value of the angle between the magnetic field and shock normal direction f θBn is obtained: the higher the value of θBn is, the larger the value of the relative density of He++ ions is behind the shock front.

The structure of the solar wind plasma flow downstream of the ramp of the interplanetary and bow shocks was studied based on the BMSW plasma spectrometer installed onboard the SPEKTR-R spacecraft. Particular attention was paid to the overshoot region, where correlated oscillations of the ion flux and magnetic field are observed. They are formed by two populations of ions: the inflowing solar wind and the beam of coherent gyrating ions. Based on the statistical analysis it was shown that overshoots form both in supercritical and subcritical shocks. It is found that maximum values of the overshoot amplitudes are significantly influenced by the angle between the shock normal and magnetic field vectors, Mach number, plasma and magnetic compression at the shock front. It was established that the oscillation wavelength determined from the magnetic field measurements onboard the WIND spacecraft, on average, coincides with the oscillation wavelength determined from the ion flux on the SPEKTR-R, while the rates of relaxation of these oscillations can greatly differ. It was also shown that the estimates of the overshoot wavelength good correlate with the convected ion gyroradius.

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.

In our study we analyzing fluctuations of the solar wind ion flux associated with the Earth bow shock using data obtained by the BMSW experiment, installed onboard the SPEKTR-R satellite. The high time resolution of the spectrometer (0.031 s for the plasma flux magnitude and direction and 1.5 s for velocity, temperature, and density) makes it possible to study fine structures in detail.From 2011 to 2019 SPEKTR-R satellite crossed the Earth bow shock many times. In our work we analyzed more than 200 bow shock crossings including multiple ones. More than half of them had fluctuations near the Earth bow shock front.It was shown that in 25% of events the frequencies of ion flux fluctuations were in the range of 3-4 Hz. In 5-7% of events the frequencies of ion flux fluctuations lay in the interval of 5-6 Hz. Just few cases had frequencies of ion flux fluctuations equal or more than 7 Hz. In other cases the frequencies of ion flux fluctuations were lower than 3 Hz or no fluctuations were observed at all.We also observed low-frequencies fluctuations about 0.1 Hz and lower. These fluctuations were also visible by the 1.5 s plasma parameters: protons density and velocity; He++ (alpha particles) density and velocity (including helium abundance).

Experimental investigations of the fine plasma structure of interplanetary shocks are extremely difficult to conduct due to their small thickness and high speed relative to the spacecraft. We studied the variations in the parameters of twice-ionized helium ions (4He++ ions or α-particles) in the solar wind plasma during the passage of interplanetary shocks and Earth’s bow shock. We used data with high time resolution gathered by the BMSW (Bright Monitor of Solar Wind) instrument installed on the SPEKTR-R satellite, which operated between August 2011 and 2019. The MHD parameters of He++ ions (the bulk velocity Vα, temperature Tα, absolute density Nα, and helium abundance Nα/Np) are analyzed for 20 interplanetary shocks and compared with similar parameters for 25 Earth bow shock crossings. Measurements from the WIND, Cluster, and THEMIS satellites were also analyzed. The correlations in the changes in helium abundance Nα/Np with the parameters βi, θBn, and MMS were investigated. The following correlation between Nα/Np and the angle θBn was found: the lower the value of θBn, the greater the drop in helium abundance (Nα/Np) falls behind the IP shock front. For Earth’s bow shock crossings, we found a significant increase in the helium abundance (Nα/Np) in quasi-perpendicular events.

The structure of the solar wind plasma flow downstream of the ramp of the interplanetary shock is studied based on the BMSW plasma spectrometer installed onboard the SPEKTR-R spacecraft. Particular attention is paid to the overshoot region, where correlated oscillations of the ion flux and magnetic field, which decaying with distance from the ramp, are observed. They are formed by two populations of ions: the inflowing solar wind and the beam of reflected ions. Based on an analysis of 26 crossings of interplanetary shock fronts, in which overshoots were observed in the value of the ion flux and the magnetic field, it is shown that overshoots form not only in supercritical shock, but also in those with Mach numbers that are less than or approach the value of the first critical Mach number. It is found that the formation and value of the overshoot amplitude in the structure of the shock front are significantly influenced by the angle between the normal to the shock front and the magnetic field vector ahead of the front, the Mach number, and the magnetic and plasma compression at the wave front. It is established that the oscillation wavelength determined from the magnetic field measurements onboard the WIND spacecraft, on average, coincides with the oscillation wavelength determined from the ion flux on the SPEKTR-R spacecraft, while the spatial scales of the oscillation-damping regions can greatly differ.

Variations in the solar wind (SW) parameters with scales of several years are an important characteristic of solar activity and the basis for a long‐term space weather forecast. We examine the behavior of interplanetary parameters over 21–24 solar cycles (SCs) on the basis of the OMNI database (https://spdf.gsfc.nasa.gov/pub/data/omni). Since changes in the parameters can be associated with both changes in the number of different large‐scale types of SW and with variations in the values of these parameters at different phases of the solar cycle and during the transition from one cycle to another, we select the entire study period in accordance with the Catalog of large‐scale SW types for 1976–2019 (see the site http://www.iki.rssi.ru/pub/omni, [Yermolaev, Nikolaeva, et al., 2009, https://doi.org/10.1134/s0010952509020014], which covers the period from 21 to 24 SCs) and in accordance with the phases of the cycles, and average the parameters at selected intervals. In addition to a sharp drop in the number of interplanetary coronal mass ejections and associated sheath types, there is a noticeable drop in the value (by 20%–40%) of plasma parameters and magnetic field in different types of solar wind at the end of the 20th century and a continuation of the fall or persistence at a low level in the 23–24 cycles. Such a drop in the solar wind is apparently associated with a decrease in solar activity and manifests itself in a noticeable decrease in space weather factors.

In our study we analyzing the fine structure of interplanetary shock wave fronts recorded by the BMSW experiment, installed onboard the SPEKTR-R satellite. The high time resolution of the spectrometer (0.031 s for the plasma flux magnitude and direction and 1.5 s for velocity, temperature, and density) makes it possible to study the internal structure of the IPs front. BMSW experiment registered 55 IPs waves from 2011 to 2019. For 21 events (where the temperature was not very high), the parameters of twice-ionized helium (He++ or α-particles) - density (absolute value and relative to protons content in the solar wind plasma), velocity, temperature. It is shown that the speed of He++ is slightly less (for about 5%) than the speed of protons, the relative density of He++ rarely exceeds 10%, and the temperature of He++ is about 2 times higher than the temperature of protons. On the IPs front, short-term and significant (up to 20%) jumps in the relative density of He++ were detected in several events. No dependence was found between Mms/proton beta and He++ density changing after IPs front. However, we detected that the lower Qbn parameter is, the more the relative density of He++ falls behind the IPs front.

The variations in the parameters of twice ionized helium ions He++ of solar wind plasma during the passage of the front of the interplanetary shock are studied. Data taken from measurements by the Bright Monitor of Solar Wind (BMSW) installed onboard SPEKTR-R satellite were used to calculate the parameters of the He++ ions: the speed, temperature, and absolute and relative density (helium abundance). It was found that the absolute density of He++ ions behind the front of the interplanetary shock increases and that the relative density decreases. The average helium abundance behind the shock front was slightly less (by 9%) than that in the unperturbed region. The change in helium abundance correlated with the parameter θBn: the lower the θBn value is, the higher helium abundance decrease behind the front of the interplanetary shock.