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.

The objective of investigation is to trace the changes of the ion density in the magnetosheath from the magnetopause to the bow shock. The theoretical interpretation is based on the magnetosheath- magnetosphere model, where the boundaries – bow shock and magnetopause, are self-consistently determined. The parameters in the magnetosheath are described by the gas-dynamic theory, while a variant of the Tsyganenko model is used in the magnetosphere, modified to compute the magnetic field in an area with arbitrarily chosen boundary. Data of the WIND satellites are used as solar wind monitoring. Good description is obtained for the considered crossing of the satellite THEMIS (Time History of Events and Macroscale Interactions during Substorms) of both the trend and ion density values of the magnetosheath.

Our investigation is based on the results of the numerical simulation, which describes the interaction of the solar wind with the Earth's magnetosphere. The 3D numerical magnetosheath-magnetosphere model is adopted for the description of this interaction. The flow in the magnetosheath is governed by Euler's equations of the ideal gas. Magnetospheric magnetic field model, which in fact is a modification of the Tsyganenko magnetic field model, is applied in the area of the magnetosphere. The solution (including plasma parameters distribution in the magnetosheath) is achieved as a result of the self-consistent interaction between the modules of the magnetosheath and the magnetosphere. For our purposes an event of satellite passage in the cusp area in the magnetosheath is chosen and we examine the variations of the parameters along the satellite trajectory. We discuss the ability of our model in description of the geometry of the magnetopause and the parameters distribution in the magnetosheath region.

Using Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations over a 10-year period from 2008 to 2017, we statistically investigate the thermodynamic properties for magnetosheath ions and their dependence on upstream interplanetary magnetic field (IMF) conditions. The thermodynamic properties for magnetosheath ions are estimated by using the polytropic index averaged over the subinterval that belongs to the same streamline ((alpha) over bar). The THEMIS observations show that the probability distribution of a for magnetosheath ions has a major peak at alpha similar to 1 (quasi-isothermal conditions) with a longer left tail down to (alpha) over bar -0 (quasi-isobaric conditions). The spatial distributions of (alpha) over bar for two different types according to IMF spiral angle (i.e., Parker spiral and ortho-Parker spiral IMF orientations) reveal that the ions in the downstream of a quasi-perpendicular shock (quasi-perpendicular magnetosheath) exhibit quasi-isothermal processes, while those in the downstream of a quasi-parallel shock (quasi-parallel magnetosheath) show (alpha) over bar lower than unity (down to (alpha) over bar similar to 0.8) implying the anticorrelation between the ion temperature and the ion number density variations. Moreover, (alpha) over bar in the quasi-parallel magnetosheath tends to decrease with increasing magnetic local time distance from the magnetic local noon. These results indicate that the thermodynamic properties for magnetosheath ions depend on the bow shock geometry (quasi-perpendicular bow shocks versus quasi-parallel bow shocks) and are presumably controlled by a variety of instabilities, waves, and turbulence in the magnetosheath.

The purpose of this research is to investigate the wide range of ion density variations in the magnetosheath. In an attempt to explain these variations the numerical magnetosheath-magnetosphere model is applied. The gas-dynamic theory describes the plasma characteristics in the magnetosheath, while in the magnetosphere a numerical magnetospheric magnetic field model is adopted. ACE spacecraft measurements are used as a solar wind monitor. The considered event of Cluster satellite passing through the magnetosheath is connected with strong ion density variation along the satellite trajectory. The results of 3D numerical modeling, presented in this paper, confirm that such variations are well represented in the frame of gas-dynamics.

We investigate the behaviour of the plasma parameters in the magnetosheath in a case when Interball-1 satellite stayed in the magnetosheath, crossing the tail magnetopause. In our analysis we apply the numerical magnetosheath-magnetosphere model as a theoretical tool. The bow shock and the magnetopause are self-consistently determined in the process of the solution. The flow in the magnetosheath is governed by the Euler equations of compressible ideal gas. The magnetic field in the magnetosphere is calculated by a variant of the Tsyganenko model, modified to account for an asymmetric magnetopause. Also, the magnetopause currents in Tsyganenko model are replaced by numericaly calulated ones. Measurements from WIND spacecraft are used as a solar wind monitor. The results demonstrate a good agreement between the model-calculated and measured values of the parameters under investigation.

This paper presents a case study of the plasma parameters in the magnetosheath, based on THEMIS measurements. As a theoretical tool we apply the self-consistent magnetosheath-magnetosphere model. A specific aspect of the model is that the positions of the bow shock and the magnetopause are self-consistently determined. In the magnetosheath the distribution of the velocity, density and temperature is calculated, based on the gas-dynamic theory. The magnetosphere module allows for the calculation of the magnetopause currents, confining the magnetic field into an arbitrary non-axisymmetric magnetopause. The variant of the Tsyganenko magnetic field model is applied as an internal magnetic field model. As solar wind monitor we use measurements from the WIND spacecraft. The results show that the model quite well reproduces the values of the ion density and velocity in the magnetosheath. The simlicity of the model allows calulations to be perforemed on a personal computer, which is one of the mean advantages of our model.

Earlier developed single fluid gas-dynamic model of solar wind–comet ionosphere interaction is applied to reveal some specifics in the morphology of the shocked “contaminated” solar wind region (cometosheath). The model is based on the Euler equations with added mass-loading, mass-loss and frictional force terms. Numerous reactions are taken into account in these terms including photoionization, charge transfer, dissociative recombination and ion-neutral frictional force. The electromagnetic terms are omitted, thus reducing the MHD single-fluid system of equations to gas-dynamic one. The used shock-fitting numerical scheme allows the separation of distinct areas formed by the considered interaction and exploration of their properties in detail. Attention is focused on the region between the shock wave and the contact surface as well as on the positions of these boundaries. Accurate examination of the distribution of density, temperature and velocity reveals spatial variations that resemble the variations registered by a number of spacecraft in the vicinity of comets. No specific comparisons with data are made at this stage. Two very first events of the Rosetta spacecraft’s crossing of the magnetic cavity boundary around Comet 67P/Churyumov–Gerasimenko are discussed using a “faux-transient” application of our steady-state model.

This paper describes an approach to a theoretical interpretation of Interball-1 satellite measurements data in two cases of the satellite’s crossings of the magnetosheath. An interpretation is made of both the measured crossings of the magnetosheath boundaries and the behavior of the registered plasma parameters. In our case, it is the value of the ion flux along the spacecraft trajectory. The magnetosheath–magnetosphere model, developed at the Institute of Mechanics, Sofia, Bulgaria, is used as a theoretical basis. It describes the interaction between the solar wind and the Earth’s magnetosphere in a simplified gas-dynamic approximation. A characteristic feature of the model is that it allows for the self-consistent description of the magnetosheath boundaries – the bow shock (BS) and the magnetopause (MP). The three-dimensional picture of the magnetosheath fluid flow is also obtained as part of the solution. The magnetosheath characteristics thus obtained are in correspondence with a given momentary state of the interplanetary medium, defined on the basis of WIND satellite data (appropriately shifted by time). The results are discussed in the context of advantages and limitations of using the gas-dynamic model for the interpretation of magnetosheath plasma measurements in the near-magnetopause magnetosheath.

Periodic comets move around the Sun on elliptical orbits. As such comet 67P/Churyumov-Gerasimenko (hereafter 67P) spends a portion of time in the inner solar system where it is exposed to increased solar insolation. Therefore given the change in heliocentric distance, in case of 67P from aphelion at 5.68 AU to perihelion at ~1.24 AU, the comet’s activity—the production of neutral gas and dust—undergoes significant variations. As a consequence, during the inbound portion, the mass loading of the solar wind increases and extends to larger spatial scales. This paper investigates how this interaction changes the character of the plasma environment of the comet by means of multifluid MHD simulations. The multifluid MHD model is capable of separating the dynamics of the solar wind ions and the pick-up ions created through photoionization and electron impact ionization in the coma of the comet. We show how two of the major boundaries, the bow shock and the diamagnetic cavity, form and develop as the comet moves through the inner solar system. Likewise for 67P, although most likely shifted back in time with respect to perihelion passage, this process is reversed on the outbound portion of the orbit. The presented model herein is able to reproduce some of the key features previously only accessible to particle-based models that take full account of the ions’ gyration. The results shown herein are in decent agreement to these hybrid-type kinetic simulations.

We utilize the IMECH numerical model of the solar wind interaction with the system magnetosheath-magnetosphere in modelling this system interaction with interplanetary magnetic clouds. The used model integrates self-consistently a 3D numerical magnetosheath model and a modified Tsyganenko magnetosphere model with numerically-computed shielding field, providing in particular a 3D magnetosheath and shock wave geometries and positions. It is demonstrated that the relatively simplified model predicts adequately the magnetosheath structure, and especially - the magnetopause behaviour, as the parameters vary with the passage of a magnetic cloud. Special attention is paid to the magnetic cloud event on 10-11 January 1997 and Interball-1 crossing from the magnetosphere to the magnetosheath.

Solar Wind-Comet Exosphere Interaction. 2. Could the Single-Fluid Gas-Dynamic Model be Applicable to the Rosetta Mission The capabilities of a single fluid gasdynamic model of solar wind-comet exosphere interaction, presented in the accompanying (Keremidarska et al.) [23], are discussed from the point of view of its potential implementation in interpreting data, expected to be obtained by ROSETTA mission instruments in plasma environments of the comet 67P/Churyumov-Gerasimenko. As an exapmle, some model's predictions of the structure and parameters' distribution in the inner coma of P/Halley are presented and compared with Giotto measurements. Special attention is paid to a possible non-traditional interpretation of the magnetic cavity boundasry, registered by Giotto magnetometer. Possible model's applications are discussed for each of the main expected stages in the evolution of the comet 76P/CG environments during ROSETTA rendezvous with the comet.

We present a new model of the magnetospheric magnetic eld. Using the nite element method, ChapmanFerraro problem is solved numerically in the considered approach. The whole magnetic eld is a sum of: the dipole eld, the eld, produced by the internal current systems (cross-tail, Birkeland, ring currents) and the eld, due to the magnetopause currents. In contrast to similar earlier models, the internal magnetospheric magnetic elds are taken from Tsyganenko data-based model. The magnetosphere boundary could be arbitrary (generally non-axisymmetric). Input model parameters are the solar wind parameters, the Dst index and the dipole tilt angle. We discuss some results, obtained in the three dimensional solution of the Neumann-Dirichlet problem, corresponding to a closed magnetosphere.

We report first comparison of the measurements of GOES magnetospheric magnetic field from geosynchronous orbit with the predictions of the magnetosphere module of the new IMECH magnetosphere magnetosheath model. The magnetosphere module of the IMECH complex model could be considered as a modification of the Tsyganenko magnetosphere magnetic field statistical model with more realistic 3D magnetopause shape and position, obtained self-consistently together with the solution of the 3D magnetosheath problem in gasdynamic approach. The pressure balance condition on the magnetopause is satisfied in this solution and the corresponding magnetopause shielding field is computed, solving the Chapmen-Ferraro problem by finite element numerical method. Thus, the resulting magnetosphere model depends on the solar wind parameters not only through the Tsyganenko's current systems, but via the shape and the position of so obtained more realistic magnetopause and shielding field. A good coincidence of the measured and predicted magnetic field values are demonstrated under real solar wind conditions.