The paper examines conditions of occurrence and typical time scales of a polarization jet by measuring ionospheric parameters from DMSP satellites (h~830 km) and using data from the ground-based ionospheric station Yakutsk (YA462) during strong and long-term geomagnetic storms. The polarization jet at the ionospheric station Yakutsk was recorded in the dusk sector at the background of substorm disturbances when the geomagnetic index SME reached values from 1000 to ~3000 nT, and, according to data from the magnetic observatory Yakutsk (YAK), there was a positive bay ~50–100 nT in the geomagnetic field H component and ~100–200 nT in its Z component. We show that the lifetime of the polarization jet or narrow troughs in ionospheric plasma in the subauroral ionosphere during strong and long-term magnetic storms can be as long as 12 hrs.

During magnetospheric substorms in the F region of the ionosphere and up to altitudes of 1000 km, a polarization jet (PJ) is developed. Measurements of energetic ring current ions on the AMPTE/CCE satellite and driftmeter data on the DMSP satellites evidence that the formation of PJ is associated with the injection of energetic ions (10–100 keV) into the inner magnetosphere during substorms. In the region of PJ development, the characteristics of the ionospheric plasma change: the plasma density decreases, sometimes by an order of magnitude, and at the same time, the plasma temperature increases significantly. In addition, simultaneously with the westward plasma drift, upward plasma drift is usually observed. The upward ion flux from the region of PJ development of 109 cm–2 s–1 is an order of magnitude greater than the average daytime ion flux from the ionosphere to the plasmasphere. Measurements on the MAGION-5 satellite in the plasmasphere on the same L-shells, where the polarization jet is recorded in the ionosphere, show an increase in the cold ion density. The density “humps” observed near the plasmapause are apparently formed due to plasma flows from the ionosphere accompanying the formation of the polarization jet. Thus, the consequences of substorms are observed throughout almost the entire magnetosphere.

В работе анализируются результаты многолетних комплексных экспериментов, выполненных на сети станций Якутского геофизического полигона и с помощью ионосферных и высоко-апогейных спутников. Наземные оптические измерения выполнялись в обсерватории Маймага (L = 3.2). Ионосферные наблюдения проводились в Якутске (L = 3.0), Жиганске (L = 4.0), Тикси (L = 5.6), Подкаменной Тунгуске (L = 3.0) и Магадане (L = 2.9) методами вертикального и наклонного зондирования с помощью высокопотенциальных двойных горизонтальных ромбических антенн. Настоящая работа суммирует физические свойства поляризационного джета с целью проведения геофизической верификация возможных механизмов его формирования. По ионограммам ионосферных станций при сопоставлении их со спутниковыми измерениями быстрых струйных течений плазмы выявлена сигнатура поляризационного джета. Это позволило использовать 15-минутные ионозондовые измерения обширной сети станций для исследования локального и быстро протекающего процесса развития поляризационного джета. Это также дало возможность провести сопоставление с измерениями энергичных ионов на спутнике AMPTE/CCE и установить, что поляризационный джет развиваются на внутренней границе кольцевого тока. По многолетним измерениям ионозондов было установлено, что поляризационный джет возникает в около-полуночном секторе на взрывной фазе суббури в области разрыва Харанга.

Based on thermal plasma measurements on the MAGION-5 and INTERBALL-1 satellites in the plasmasphere boundary layer, similar recurring changes in the proton density were identified depending on the L -shell. Such density variations have the following characteristic features: (a) density variations occur sharply, on the density profile—the dependence of density on L or on geomagnetic latitude λ—they have a sawtooth nature, and the density of protons at the peaks (maxima) of variations exceeds that at the minima of variations by two to eight times; (b) the characteristic size of variations in the radial direction in the plane of the geomagnetic equator is ~0.15 R E or ~1000 km; (c) sawtooth changes in proton density in the plasmasphere boundary layer can span at least 90° in longitude; (d) regular variations in plasma density were observed at geomagnetic latitudes up to 30°, and this latitude is limited to the orbits of satellites whose data were used for the analysis. Sawtooth variations in thermal plasma density are apparently related to spatial structures that evolve but persist in the plasmasphere boundary layer, at least over the course of a day. Plasma inhomogeneities were observed in fairly quiet or slightly disturbed geomagnetic conditions. The considered inhomogeneities are probably a consequence of the interchange or quasi-interchange instability developing in the plasmasphere boundary layer.

Cold (<1 eV) plasma measurements in the Earth’s inner magnetosphere are used to deduce proton density and temperature distributions, as well as the potential of a spacecraft with a wide-angle analyzer onboard the INTERBALL-1 spacecraft. We analyzed these quantities recorded near the plane of the geomagnetic equator. Quantitative expressions are obtained for the proton density and temperature distribution in the magnetic equatorial plane of the plasmasphere in the entire range of the McIlwain L-parameter (distance to the Earth center in units of the Earth’s radii in the equatorial plane). The temperature of protons in the plasmasphere significantly depends on the local time and is determined mainly by the plasma temperature in the underlying ionosphere. The rate of increase in the proton temperature in the plasmasphere relative to the electron temperature in the ionosphere depends on the phase of the solar activity cycle.

— 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.

Doppler measurement data from the Yakutsk subauroral ionospheric station have been used to reveal for the first time new and previously unknown dynamic phenomena during the development of the polarization jet. This study of horizontal and vertical velocities of ionospheric drifts reveals that the peaks of vertical and horizontal velocity components do not always coincide during the observation of a polarization jet. The horizontal plasma drift velocities are ~300–600 m/s on average (there are events with velocities of 900–1000 m/s). The vertical drift velocities are 30–50 m/s on average (there are events with velocities of 100–150 m/s). Analysis of ground-based ionospheric data has revealed that all events with the development of the polarization jet over Yakutsk were uniformly divided into four cases. In the first case, the vertical velocities in the polarization jet band reached a maximum simultaneously with horizontal velocities. In the other two cases, the times of the vertical velocity peaks are shifted to both sides of the reference time by ±1 h. In the latter case, the vertical velocities have similar peaks on both sides of horizontal velocity peaks.

Complex optical and ionospheric measurements in the region of the formation of red arcs accompanying the polarization jet development are analyzed. Optical measurements were done at subauroral station Maimaga, and ionospheric measurements were fulfilled at subauroral stations Yakutsk and Zhigansk. Spatial location and intensity of red-arcs were detected by the meridional scanning photometer. The temperature of the neutral atmosphere was recorded by Fabry-Perot interferometer. It is shown that the temperature of the neutral atmosphere increases in the red arc region and changes in accordance with variations in the emission. On 02 December 1989 the neutral temperature increased by 500 K in the red arc relative to the undisturbed level determined for quiet days during the month. This evidences on the strong heating process in the red arc region. According to ionospheric and satellite data on 18 February 1999 the red arc was observed simultaneously with polarization jet development - fast westward plasma drift in the poleward electric field. The magnitude of this electric field was 50-80 mV/m. Due to frictional interaction of ions and neutrals, ions were heated up to 5000-6000 K and neutrals gain energy of some hundreds degrees.

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.

The paper has presented a study of the dependence of the H + ions concentration in the plasmasphere on geographic longitude. A vast database of measurements of the cold plasma density by the Alpha-3 instrument on board the INTERBALL-1 satellite has been used for the study. Based on these measurements, a dependence of the H + ions concentration in the filled magnetic flux tube in the plasmasphere in the equatorial plane under quiet geomagnetic conditions has been obtained as a function of geographic longitude. Studies have been performed for two seasons, summer and winter. It has been shown that, during the summer in the near-midnight sector, the minimum in the H + concentration falls within geographic longitudes of 270°–315°. The ratio of the concentration of H + ions at various longitudes could reach a factor of three. During the winter, in the near-noon sector, the maximum of the H + ions concentration falls within longitudes of 180°–225°, whereas the concentration ratio could reach a factor of 2.2.

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.