— On January 21, 1972, the Mars 3 satellite recorded a strong (~27 nT) regular magnetic field in the region of the spacecraft’s closest approach to the dayside of Mars. Many hypotheses about the nature of this field have been discussed. Only in 1998 did the Mars Global Surveyor ( MGS ) mission manage to measure the magnetization of the Martian surface and clarify the features of the complex Martian magnetosphere. Comparison of the Mars 3 data with the MGS data has shown that, in 1972, a strong and regular magnetic field was observed with the same direction and exactly over the region of the strongest magnetization of the Martian crust in the southern hemisphere of the planet. Thus, Mars 3 recorded the magnetic field of the Martian crust about 25 years before its discovery. Large regions of crustal magnetization in the southern hemisphere at a great distance from the planet generate a significant dipole component in the magnetic field around Mars. Thus, Mars is a unique planet in the Solar System, the magnetosphere of which is formed by the interaction of the solar wind with the intrinsic magnetic field of the crust and with the ionosphere of the planet. The hypothesis that the Martian magnetosphere had a hybrid nature was put forward earlier according to the data of the Phobos 2 spacecraft, although it was associated with the existence of an internal dipole field. It is also shown that the MAVEN spacecraft data confirm the suggestion, drawn from the Phobos 2 data, that Mars has a denser hot corona than was previously assumed, and these data are in a good agreement with the Phobos 2 results concerning ion acceleration in the tail of the Martian magnetosphere.

In studies of physical processes near planetary bow shocks, empirical models of the latter are usually used. While computational magneto‐hydrodynamics (MHD) or kinetic models of bow shocks are often more accurate, their computationally extensive nature limits their applicability to routine analysis of large volumes of data. We suggest an analytical model of the bow shock position based on MHD calculations and accurate analytical solutions. The analytical expressions for the bow shock position and shape include the following parameters: The distance of the bow shock nose point from the planet, radii of curvature and bluntnesses of the shock surface at this point and a parameter describing the transition to the asymptotic downstream slope of the shock. It is shown that for an analytical description of the surface of the shock, it is sufficient to approximate its radius of curvature and bluntness in two perpendicular planes. Another parameter used in this model is the bow shock skewing angle, appearing when the interplanetary magnetic field directed at an angle with respect to the solar wind velocity. This parameter naturally vanishes when the magnetic field of the solar wind is directed either parallel or perpendicular to the velocity vector. The exact analytical solution for the asymptotic downstream slope of the MHD Mach cone is modified to take into account the skewing angle of the bow shock.

Study of physical processes in plasma near planets often requires knowledge of the position and shape of the planetary bow shock. Empirical models are usually used since theoretical MHD and kinetic models consume too much computer time and cannot be used to track fast processes. M.I. Verigin proposed a semi-empirical approach based on the use of exact theoretical expressions with a small number of parameters, which have a clear physical meaning. These parameters are estimated by fitting experimental data or detailed MHD calculations. A model of the bow shock near an arbitrary-shaped obstacle has previously been developed for a gas-dynamic flow. This model can be applied to any sonic Mach numbers and large values of the Alfven Mach number. In addition, the asymptotic Mach cone - the angle of inclination of the shock wave at an infinite distance from the planet - has been calculated analytically in the MHD approximation. In this paper, we propose a model of the bow shock for any direction of the magnetic field with respect to the upcoming flow and for any Mach numbers. Parameters of the model are the distance of the nose point from the obstacle, radius of curvature and bluntness of the bow shock at the nose point, a parameter related to the transition to the asymptotic downstream slope of the shock, and a skewing angle appearing when the interplanetary magnetic field is directed at an angle to the solar wind velocity.

An analytical semiempirical model of the bow shock based on theoretical MGD calculations, accurate analytical solutions, and experimental data continues to be developed. The model parameters have a clear physical meaning. For cases in which the magnetic field of the solar wind is directed along its velocity or is perpendicular to the velocity vector, analytical expressions that allow calculating the parameters of the bow shock-the distance to the subsolar point, the radius of the curvature, and the bluntness at the subsolar point-are obtained via renormalization of the previously developed detailed gas-dynamic model. For the case in which the magnetic field vector is perpendicular to the solar wind velocity vector, it is shown that it is sufficient for an analytical description of the bow shock surface to approximate its parameters in two perpendicular planes.

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 paper, the effect of the magnetosheath boundaries on the forms of frequency spectra of ion flux fluctuations is analyzed based on statistics. In addition, variance in the spectrum characteristics are considered, such as spectral slope at the magnetohydrodynamic (MHD) and kinetic scales, as well as the frequency of transition between these scales when the satellite crosses the magnetosheath. The analysis is based on measurement of the ion flux by the Fast Solar Wind Monitor (BMSW) onboard the Spektr-R satellite with a time resolution of 31 ms. It is shown that the probability of observing spectra of the particular type greatly varies upon crossing of the magnetosheath: standard spectra with two slopes and a distinct breakpoint are observed in most cases in all parts of the magnetosheath, and the probability of their observation is slightly higher upon the approach to the magnetopause; spectra with a peak in the region of transition between the scales (MHD and kinetic) are more often observed closer to the bow shock, and spectra with a plateau in the region of transition between the scales are usually observed closer to the magnetopause. It is revealed that the spectra at the MHD scales immediately behind the bow shock are described by a power function with index –1.3 on average, which noticeably differs from the index of –5/3 predicted by the classical theories. The spectra at the kinetic scales immediately behind the shock wave become steeper than in the solar wind and slightly flatten on the approach to the magnetopause.

In this paper, the correlation coefficient between the ion fluxes in the solar wind and the magnetosheath is analyzed with the use of data of two satellites of the THEMIS mission and the THEMIS/Spektr-R satellites obtained in 2008 and 2011−2014, respectively. We have distinguished the conditions in which a high level of correlation between the measurements in the solar wind and the magnetosheath is observed, i.e., the correlation coefficient exceeds 0.7. As key factors, we consider both direct parameters of the solar wind, such as the density, the magnetic field magnitude, the magnetosonic Mach number, and the ratio β of the thermal pressure to the magnetic, and a more general factor—the type of large-scale structure of the solar wind. In addition, the effect of the satellite location in the magnetosheath relative to its boundaries—the bow shock and the magnetopause—on the correlation level is considered. It has been shown that, in roughly one third of cases, the plasma structures of the solar wind undergo a strong modification at the bow shock and in the magnetosheath, which results in a low correlation level corresponding to a correlation coefficient of less than 0.5; a high correlation level is observed in half of cases, i.e., the plasma structures are weakly disturbed. It has been determined that (1) the low correlation level in the magnetosheath behind quasi-perpendicular bow shock is more often observed near the magnetopause than in region just behind the bow shock, (2) the probability of observations of a high correlation level is independent of the profile shape of the quasi-perpendicular bow shock, and (3) the high correlation is more probable for the events corresponding to the solar wind of the Corotating Interaction Region (CIR) type than for those with the other solar wind types observed in the considered period.

The in situ cold plasma measurements onboard MAGION 5 were carried out with very good time resolution, and this permitted to analyze thin plasmasphere boundary layer (PBL) near the plasmapause. In this layer the plasma density N is decreasing exponentially with L: N~exp((LPP − L)/WB), where WB corresponds to the characteristic width of the PBL, the distance in L within which the density varies by a factor of e, and LPP is the position of the plasmapause. The density in the boundary layer is inversely proportional to the volume of the unit magnetic flux tube, whereas its width is proportional to the volume of magnetic flux tube. The characteristic width of the PBL linearly depends on the time elapsed since the most recent maximum value of KP. Empirical relation for the dependence of the PBL width on most recent maximum value of KP and on the lapse time between this maximum and the plasmapause observations is proposed.

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.

From the data on the cold plasma measurements onboard the INTERBALL-1 spacecraft (1995–2000), the plasmapause positions determined from the most frequently used formal criterion—a fivefold or higher decrease in plasma density with an increase in the L-shell by 0.5—and visually from the measured energy spectra of thermal protons have been analyzed and compared. The difference in the results of the both empiric techniques makes it possible to estimate the thickness of the boundary layer of the plasmasphere. The model of the Earth’s plasmasphere developed earlier by the authors (Verigin et al., 2012; Kotova et al., 2015) based on the theoretical expressions makes it possible to reconstruct the plasma distribution throughout the plasmasphere from the measurements along a single pass of the orbiter and to find the plasmapause position defined as the last closed stream line. Comparison of the plasmapause position obtained with empirical techniques to the position of this boundary calculated with physically based models of the plasma distribution in the plasmasphere has shown that the modeled position of the plasmapause approximately coincides with that determined from the formal criterion described above.

AbstractIt is generally accepted to use the solar wind ram pressure ρV2 and the IMF Bz component for empirical description of the geo-magnetopause position and shape. A specific feature of the present paper is not to use the solar wind ρV2 but the thermal Pth and magnetic field Pmag pressures adjacent to the magnetopause for proper modelling. These pressures are deduced from the results of 3-D MHD runs and analytic solutions for post bow shock MHD flow in Lagrangian variables. The magnetopause shape variation due to Bz component changes the so called ‘doubling factor’ fd, which can be analytically deduced from a Tsyganenko magnetospheric field ellipsoidal model. Including all the above effects in our analytical model leads to a good description of ‘rapid’ magnetopause approach to the Earth for southward IMF and to its ‘stagnant’ behaviour with the increase of northward IMF component.

The Interhelioprobe mission aims to investigate the inner heliosphere and the Sun from close distances (up to 0.3 AU) and from out of the ecliptic plane (up to 30°). In this paper we present the relevance of the mission and its main scientific objectives, describe the scientific payload, ballistic scenario and orbits of the spacecraft. Possibilities of scientific cooperation with other solar and heliospheric space missions are also mentioned.

The data base of the Alpha‐3/Interball‐1 measurements was used for semiempirical 3‐D modeling of plasma distribution inside the plasmasphere for quiet (stationary) geomagnetic conditions. A 2‐D model describing the density distribution in the meridional plane is based on equations of the plasma distribution in the plasmasphere for the cases of thermal equilibrium and collisionless initial partial filling of plasmaspheric shells. This 2‐D model is then expanded into a 3‐D one using simple equations for the shape of the plasmapause and density behavior in the equatorial plane along the convection streamline. The model has six free parameters with clear physical meaning. This modeling approach can be applied for extrapolation of data from magnetospheric satellites with very different orbits into the entire plasmasphere.

The data processing technique was developed for thermal plasma measurements by wide-angle plasma analyzers, which was successfully used for the Interball mission instruments. This technique considers the effect of spacecraft potential on plasma measurements. When the spacecraft enters the optical shadow of the Earth, the evaluated spacecraft potential suddenly drops, but no abrupt changes of plasma density or temperature are observed. Often observed decrease in temperature of protons in the Earth's shadow is actually associated with shading of ionospheric feet of magnetic field line passing through the spacecraft. This suggests that ionospheric photoelectrons are an important heat source for the plasmasphere. Besides, the Interball 1 data suggest that photoelectrons coming from the nearest ionosphere are more effective in plasmaspheric ion heating than photoelectrons from the conjugate hemisphere.