Results are presented from numerical modeling to investigate the effect the Earth’s relief has on the circulation of the lower and middle atmosphere. The main focus is on the effect an isolated mountain array has on the circulation of the lower and middle atmosphere in its vicinity. Mountains and rocks covering the Kerguelen archipelago are selected to represent the isolated mountain array.

Представлены результаты моделирования прохождения негармонических сигналов от расположенной на поверхности Земли антенны через верхний слой литосферы и отражения этих сигналов от различных неоднородностей в литосфере в случае, когда на антенну подается видеоимпульсный сигнал специальной формы. Используемая в работе модель основана на явной схеме численного интегрирования уравнений Максвелла. В этой схеме электрическое и магнитное поля вычисляются в одни и те же моменты времени в одинаковых узлах пространственной сетки, а также используется расщепление по пространственным направлениям и физическим процессам. В работе изучается, какую информацию о характере неоднородности литосферы можно извлечь из формы отраженного сигнала. Также исследуется влияние параметров видеоимпульсного сигнала на амплитуду и форму отраженных от типичных неоднородностей литосферы сигналов. Показано, что некоторые типы неоднородностей можно определить по форме отраженного сигнала.

Results are presented from numerical modeling to investigate the impact the Earth’s relief has on the circulation of the Antarctic’s lower and middle atmosphere. Modeling is done for the summer season in the Southern hemisphere (January). Results suggest the relief of the planet, and particularly the mountains of the Antarctic continent, notably influence the circulation of the Antarctic’s lower and middle atmosphere.

The paper presents the results of the modeling of VLF radio waves propagation in horizontally inhomogeneous region of the high-latitude Earth-ionosphere waveguide during different types of the geomagnetic disturbances. The frequencies of the model source of signal correspond to the frequencies of the long-distance navigation radio system RSDN-20 "Alpha " constantly broadcasting in the VLF range in the Russian Federation. It is considered the geomagnetic storm on 24 January 2012 and geomagnetic substorm on 11 December 2015. Electron density profiles and collision rates of electrons with neutrals are taken from the measurements of EISCAT radar in Tromso and EISCAT 42m radar on Svalbard. The numerical experiments were conducted with a highly horizontally inhomogeneous electron density in the ionosphere. It is shown that the amplitudes and phases of the VLF signals at these frequencies show a noticeable reaction to changes in the ionospheric parameters during the considered geomagnetic disturbances. Calculations show that changes in amplitude of RSDN-20 "Alpha " signals caused by the action of the Earth's magnetic field and horizontal inhomogeneities depend on the direction of signal propagation relative to the Earth's magnetic field vector and cannot be reversed if the direction of propagation changes to the opposite. The results of the numerical experiment were compared with the corresponding characteristics of the RSDN-20 signals calculated from the observations of electromagnetic signals at the Lovozero observatory for the case on 11 December 2015.

In this paper, we study the amplitude and phase characteristics of VLF signals of an anthropogenic origin during solar proton events using the methods of a computational experiment. We consider the events of October 30, 2003 and January 23, 2012. Electron density profiles are plotted using data from the VHF EISCAT incoherent scatter radar located in Tromsø, Norway. Based on the processed data of computational experiments, that under the conditions of solar proton events, mainly amplitude distortions of VLF signals were shown to be observed while there is a frequency dependence of the magnitude of distortions of the signals of the RSDN-20 long-range navigation radio system. The signal phases of the RSDN-20 system are less affected by weak solar proton events. The effect of the lower boundary of the Earth-ionosphere waveguide in the cases of propagation of signals from the RSDN-20 system over the surface of land and ocean during a solar proton event was studied.

A numerical model is used to study the possibility of a thin current sheet formation in the near-Earth magnetotail in the growth phase of a substorm for a wide range of parameters of longitudinal countermoving ion flows that create current sheet. The simulation results make it possible to conclude that the current sheet can be formed by oxygen ion flows of ionospheric origin in cases where the proton fluxes can be neglected or they are rather weak. Such conditions are realized in the Earth’s magnetosphere during periods of increased geomagnetic activity. In addition, the influence of electron pressure anisotropy on the steady-state configuration of the considered current sheet is investigated.

Results are presented from numerically modeling the initial stage of the origination of polar lows in the troposphere in the vicinity of an Arctic front. It is found that convexities in an Arctic front profile can result in polar lows with different properties in the high-latitude atmosphere.

A numerical model is used to show that under disturbed conditions of the Earth’s magnetosphere, a thin current sheet can form in the near part of the magnetotail. The sheet is caused by counter-flows of oxygen ions of ionospheric origin when fluxes of magnetospheric protons are negligible, relative to ionic ones. Equilibrium configurations of such a current sheet are obtained that are in complete agreement with experimental data.

Results are presented from numerically modeling areas on the Earth’s surface within the Barents Sea that include single-jump beam trajectories of HF-band radio waves propagating from a transmitter located at middle latitudes under substorm conditions on December 24, 2014. The parameters of the ionosphere are determined using the empirical GDMI model, corrected for data on auroras and the full electronic content measured using signals from GPS satellites flying over the areas where the auroras were observed. An analysis is performed of changes in the possibilities of single-jump HF radio communication between the Barents Sea and mid-latitude regions during auroral eruptions and calm conditions.

Results are presented from modeling the general circulation of the Earth’s atmosphere in the 0 to 80 km range of altitudes in mid-January usinf a non-hydrostatic model. The field of solar and thermal radiation is calculated with high accuracy in the model. The model reproduces surface cells of vertical meridional circulation over oceans, large-scale vortices, mountain leeward waves, the rise of the tropopause over the winter polar region, and circumpolar vortices and warming in the upper stratosphere and lower mesosphere in the polar region of a winter hemisphere.

We suggest a solution of the problem of the description of magnetic and electric fields occurring during large-scale nonradiative processes in the collisionless space plasma. The key idea is that the quasi-neutrality condition and the field-aligned force equilibrium of electrons should be taken into account. Equations describing the plasma are divided into two parts, namely, a system of transport equations which describes the plasma motion, and a system of equations for fields. The fields are defined in the instantaneous action approximation via the current spatial distributions of hydrodynamic plasma parameters and boundary conditions obtained from the system of elliptic equations containing no partial time derivatives. Three forms of the generalized Ohm’s law corresponding to different levels of plasma magnetization are considered. It is shown that, depending on the form of a system of transport equations derived for each plasma component, five key variants of the equation system describing the plasma can be obtained from the three forms of the Ohm’s law. The first form of the generalized Ohm’s law refers to the general case in which all plasma components unmagnetized and the system of transport equations represents the Vlasov equations for each plasma component. The second form of the Ohm’s law corresponds to the case of unmagnetized ionic plasma components, while electrons are magnetized and their pressure tensor is expressed through their longitudinal and transverse pressures as well as through the magnetic field. In the latter case two variants of the system of transport equations are possible, and the ions are described by Vlasov equations in both of them. In the first variant, the electrons are described by the Vlasov equation in the drift approximation. In the second variant, the electrons are described by the system of Chew–Goldberger–Low equations of magnetogasdynamics. The third variant of Ohm’s law corresponds to the case in which all plasma components are magnetized, and the pressure tensor of each component is replaced by its expression through the longitudinal and transverse pressure, as well as through the magnetic field. In this case, two variants of the transport equation system are also possible. In the first variant, each component is described by the Vlasov equation in the drift approximation. In the second variant, each component is described by the system of the Chew–Goldberger–Low equations of magnetogasdynamics.

A new model of the general circulation of the atmosphere of Titan is discussed. This model is based on numerical grid integration of the complete equations of gas dynamics with a fine spatial resolution. The relaxation approximation is used to calculate the power of radiation heating and cooling the atmospheric gas. The results of simulation of the general atmospheric circulation of Titan at equinox with this model are presented and analyzed.

A new explicit scheme for the numerical integration of Maxwell’s equations in isotropic and anisotropic dielectrics and conductors is presented. In this scheme, the electric and magnetic fields are calculated at the same instants and at the same nodes of the spatial grid with splitting by spatial directions and physical processes. The scheme is conservative, monotonic, second-order accurate in time, and third-order accurate in spatial variables. In the course of simulating the propagation of low-frequency signals in the Earth-ionosphere waveguide, the scheme allows using a significantly bigger time integration step than the widely used finite-difference time domain method for the same accuracy.

Crossings of the heliospheric current sheet (HCS) at the Earth’s orbit are often associated with observations of anisotropic beams of energetic protons accelerated to energies from hundreds of keV to several MeV and above. A connection between this phenomenon and the occurrence of small-scale magnetic islands (SMIs) near reconnecting current sheets has recently been found. This study shows how pre-accelerated protons can be energized additionally due to oscillations of multiple SMIs inside the ripple of the reconnecting HCS. A model of the electromagnetic field of an oscillating 3D SMI with a characteristic size of ~0.001 AU is developed. A SMI is supposed to be bombarded by protons accelerated by magnetic reconnection at the HCS to energies from ~1keV to tens of keV. Numerical simulations have demonstrated that the resulting longitudinal inductive electric fields can additionally reaccelerate protons injected into a SMI. It is shown that there is a local “acceleration” region within the island in which particles gain energy most effectively. As a result, their average escape energies range from hundreds of keV to 2 MeV and above. There is almost no particle acceleration outside the region. It is shown that energies gained by protons significantly depend on the initial phase and the place of their entry into a SMI but weakly depend on the initial energy. Therefore, low-energy particles can be accelerated more efficiently than high-energy particles, and all particles can reach the total energy limit upon their escape from a SMI. It is also found that the escape velocity possesses a strong directional anisotropy. The results are consistent with observations in the solar wind plasma.