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.

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.

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 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.

This chapter contains sections titled: Introduction Corpuscular and Optical Umbra, Corpuscular Penumbra Magnetosheath and Near-Planetary Shock Wave Discussion Conclusions

Based on experimental data obtained in 1995–2000 on board the INTERBALL-1 spacecraft using the ALPHA-3 instrument, a semi-empirical two-dimensional model of the Earth plasmasphere is developed, which allows for the plasma distribution in the entire meridional plane to be restored from the temperature and proton density measurements along the satellite orbit. The model has also been tested using the data of the IMAGE spacecraft. The model uses theoretical expressions (Lemaire and Schere, 1974) that describe the plasma distribution in the plasmasphere for the cases of thermal equilibrium and collisionless initial partial filling of plasmaspheric shells; therefore, the parameters of the constructed model have a clear physical meaning and make it possible, in particular, to estimate the degree of plasmasphere filling.

Based on the thermal plasma measurements in the Earth's inner plasmasphere on the INTER-BALL-2 and MAGION-5 satellites it has been indicated that the plasmaspheric ion temperature as a rule decreases during the main phase of magnetic storms; in this case the plasma density increases or remains at the level typical of undisturbed conditions. The physical mechanism by which the ion drift during a magnetic storm results in a temperature decrease is described. It is shown that the third adiabatic invariant also remains in processes with a characteristic time shorter than the period of charged particle drift around the Earth for cold equatorial plasma. The constructed model of the drift shell displacement from the Earth caused by a decrease in the magnetic field in the inner magnetosphere during the development of a magnetic storm satisfactorily describes the decrease in the proton temperature near the equatorial plane.

Based on the magnetopause observations near the Earth by the Prognoz/Interball satellites in 1972–2000, the empirical model of this boundary has been proposed, and the magnetopause behavior at different parameters of the oncoming solar wind has been studied. For the first time, it has been detected that the Earth’s magnetopause is compressed by ∼5% in the direction perpendicular to the plane including the vectors of the solar wind velocity and IMF. At the same time, any dependence of the subsolar magnetopause position on the IMF B z component has not been revealed in the Progrnoz/Interball data. The proposed magnetopause model can be used to model the position and shape of the near-Earth bow shock.

Depleted narrow (localized in longitude) regions (field tubes) in the plasmasphere, recently discovered in He+ radiation measurements on the IMAGE spacecraft, were first directly observed by the Magion-5 satellite. The low-density regions (notches) occupy <∼ 10–30° in longitude and extend from L ∼ 2–3 to the plasmasphere boundary in neighboring plasmasphere regions with larger densities. The Magion-5 data give evidence that in the low-density regions temperature is enhanced as compared to the neighboring denser plasmasphere regions. Formation of notches in the plasmasphere is, apparently, associated with AE intensification during weak magnetic storms, while strong magnetic storms usually result in the overall reduction of plasmasphere dimensions. However, even a strong magnetic storm on April 6–7, 2000 (max Kp = 9-and min Dst ∼ −290 nT), but accompanied by an isolated AE impulse, resulted in a density decrease only in the longitudinally limited post-midnight sector of the plasmasphere.

The thermal structure of night-time plasmasphere is examined on the basis of some results of measurements of the distribution of concentration n(p) and temperatures T-p of cold plasma in the Earth's plasmasphere. The results were obtained aboard the SA << Interball-2 >> (<< Auroral probe >>) in September 1996 and the satellite << Magion-5 >> in December 2001. It is found that night-time temperatures, unlike day-time ones, strongly depend on the geomagnetic activity level: the values of temperature and, possibly, its height gradient diminish with increasing the activity. In quiet geomagnetic conditions the increase of T-p with increasing height (or L-parameter) was observed regularly. For example, at a height of 5000 km 1600 < T-p < 2800 K and at a height of 10000 km 3000 < T-p < 4600 K. In this range of heights, middle gradient of temperature is 0.3 K/km for geomagnetic latitude -4 degrees < lambda < 40 degrees. Increase of T-p in peripheral part of plasmasphere and in plasmapause, obviously, is related to intrusion of streams of keV-particles from magnetosphere to plasmasphere. Some experimental data on variations of distribution of T-p(L) in night-time plasmasphere are given: before the beginning of the storm of 26 September 1996, during the main phase and in the phase of renovation. The reasons of the variations are discussed with allowance made for the corotation of cold plasma in the Earth's power tubes. Large-scale region with the negative gradient of temperature on L > 2, which was regularly observed by the SA << Auroral probe >> in the day-time sector of plasmasphere during the period close to the minimum of solar cycle, was not detected in the night-time sector in September 1996. However, in 1999-2001 the region with the negative gradient of temperature in the night-time sector was observed by the satellite << Magion-5 >> once or twice.

We consider the results of measurements of density and temperature of cold plasma in the dayside sector of the plasmasphere. The measurements were made by Interball-1 (Tail Probe) in November 1995, by Interball-2 (Auroral Probe) in August 1996 (the periods close to the solar cycle minimum), and by the Magion-5 satellite in June 2000 (this period is close to the solar cycle maximum). It was shown by the measurements in the dayside sector of the plasmasphere that, contrary to expectations of model distributions of temperature in the plasmasphere [1, 2], under quiet geomagnetic conditions the temperature of hydrogen ions of the cold plasma filling the plasmasphere was observed to increase at altitudes 5000 km < H < 10000 km. Its altitude gradient was equal to ∼0.5 deg/km, the geomagnetic latitude being variable within the limits 10° < λ < 40°. The maximum values of temperature of protons, as measured by Tail Probe and Auroral Probe deep in the plasma-sphere, were equal to ∼4000–6000 K. According to the data obtained by the Magion-5 satellite in the depth of the plasmasphere, these temperatures varied within the limits 7500–8500 K. These results can be considered as some indication of a dependence of the plasmasphere thermal structure on the phase of the solar cycle. In the region 2.5 < L < 5 and at geomagnetic latitudes λ < 40°, drops of the ion temperature were regularly observed with values reaching ∼2000 K.