Lunyushkin S.B., Mishin V.V., Karavaev Yu.A., Penskikh Yu.V., Kapustin V.E. «Studying the dynamics of electric currents and polar caps in ionospheres of two hemispheres during the August 17, 2001 geomagnetic storm» Солнечно-земная физика, 5, № 2, с. 17-29 (2019)

The magnetogram inversion technique (MIT), developed at ISTP SB RAS more than forty years ago, has been used until recently only in the Northern Hemisphere. In recent years, MIT has been improved and extended to make instantaneous calculations of 2D distributions of electric fields, horizontal and field-aligned currents in two polar ionospheres. The calculations were carried out based on one-minute ground-based geomagnetic measurements from the worldwide network of stations in both hemispheres (SuperMAG). In this paper, this extended technique is used in the approximation of uniform ionospheric conductance and is applied for the first time to calculations of equivalent and field-aligned currents in two hemispheres through the example of the August 17, 2001 geomagnetic storm. We have obtained the main and essential result: the advanced MIT-ISTP can calculate large-scale distributions of ionospheric convection and FACs in the Northern (N) and Southern (S) polar ionospheres with a high degree of expected hemispheric similarity between these distributions. Using the said event as an example, we have established that the equivalent and field-aligned currents obtained with the advanced technique exhibit the expected dynamics of auroral electrojets and polar caps in two hemispheres. Hall current intensities in polar caps and auroral electrojets, calculated from the equivalent current function, change fairly synchronously in the N and S hemispheres throughout the magnetic storm. Both (westward and eastward) electrojets of the N hemisphere are markedly more intense than respective electrojets of the S hemisphere, and the Hall current in the north polar cap is almost twice as intense as that in the south one. This interhemispheric asymmetry is likely to be due to seasonal conductance variations, which is implicitly contained in the current function. From FAC distributions we determine auroral oval boundaries and calculate magnetic fluxes through the polar caps in the N and S hemispheres. These magnetic fluxes coincide with an accuracy of about 5% and change almost synchronously during the magnetic storm. In the N hemisphere, the magnetic flux in the dawn polar cap is more intense that that in the dusk one, and vice versa in the S hemisphere. These asymmetries (dawn-dusk and interhemispheric) in the polar caps are consistent with the theory of reconnection for IMF B_y>0 and with satellite images of auroral ovals; both of these asymmetries decrease during the substorm expansion phase.

Lunyushkin S.B., Mishin V.V., Karavaev Yu.A., Penskikh Yu.V., Kapustin V.E. «Studying the dynamics of electric currents and polar caps in ionospheres of two hemispheres during the August 17, 2001 geomagnetic storm» Солнечно-земная физика, 5, № 2, с. 17-29 (2019)

The magnetogram inversion technique (MIT), developed at ISTP SB RAS more than forty years ago, has been used until recently only in the Northern Hemisphere. In recent years, MIT has been improved and extended to make instantaneous calculations of 2D distributions of electric fields, horizontal and field-aligned currents in two polar ionospheres. The calculations were carried out based on one-minute ground-based geomagnetic measurements from the worldwide network of stations in both hemispheres (SuperMAG). In this paper, this extended technique is used in the approximation of uniform ionospheric conductance and is applied for the first time to calculations of equivalent and field-aligned currents in two hemispheres through the example of the August 17, 2001 geomagnetic storm. We have obtained the main and essential result: the advanced MIT-ISTP can calculate large-scale distributions of ionospheric convection and FACs in the Northern (N) and Southern (S) polar ionospheres with a high degree of expected hemispheric similarity between these distributions. Using the said event as an example, we have established that the equivalent and field-aligned currents obtained with the advanced technique exhibit the expected dynamics of auroral electrojets and polar caps in two hemispheres. Hall current intensities in polar caps and auroral electrojets, calculated from the equivalent current function, change fairly synchronously in the N and S hemispheres throughout the magnetic storm. Both (westward and eastward) electrojets of the N hemisphere are markedly more intense than respective electrojets of the S hemisphere, and the Hall current in the north polar cap is almost twice as intense as that in the south one. This interhemispheric asymmetry is likely to be due to seasonal conductance variations, which is implicitly contained in the current function. From FAC distributions we determine auroral oval boundaries and calculate magnetic fluxes through the polar caps in the N and S hemispheres. These magnetic fluxes coincide with an accuracy of about 5% and change almost synchronously during the magnetic storm. In the N hemisphere, the magnetic flux in the dawn polar cap is more intense that that in the dusk one, and vice versa in the S hemisphere. These asymmetries (dawn-dusk and interhemispheric) in the polar caps are consistent with the theory of reconnection for IMF B_y>0 and with satellite images of auroral ovals; both of these asymmetries decrease during the substorm expansion phase.

Leonovich L.A., Tashchilin A.V., Lunyushkin S.B., Karavaev Yu.A., Penskikh Yu.V. «Studying 630 nm atomic oxygen emission sources during strong magnetic storms in the night mid-latitude ionosphere» Солнечно-земная физика, 5, № 2, с. 35-41 (2019)

We analyze significant increases in 630 nm atomic oxygen night emissions during very strong geomagnetic storms, using optical measurements, theoretical modeling, and magnetogram inversion technique (MIT) data. It is shown that during strong magnetic storms when electron precipitation equatorial boundary at the night sector expands up to ∼40°, the interaction of energetic electron flux with thermospheric components may cause extreme increases in the 630 nm emission intensity. Model calculations of the red line intensity show good agreement with observational data. Using the November 20, 2003 magnetic storm as an example, we have found that oxygen atom collisions with thermal Maxwell and superthermal electrons make a major contribution to the integral emission intensity. Thermospheric density variations during the magnetic storm significantly affect the red line generation.

Кузин С.В., Кириченко А.С., Steslicki M., Sylwester J., Siarkowski M., Szaforz Z., Plocieniak S., Bakala J., Barylak J., Podgorski P., Scislowski D., Kowalinski M., Богачев С.А., Перцов А.А. «Комплекс SOLPEX для исследования излучения Солнца в мягком рентгеновском диапазоне волн» Журнал технической физики, 89, № 12, с. 1832-1835 (2019)

В комплекс SOLPEX входят 2 инструмента, для регистрации мягкого рентгеновского излучения Солнца, входящих в аппаратуру "КОРТЕС", которая будет установлена на борту Международной космической станции. Первый – быстровращающийся многокристальный брэгговский спектрометр, предназначенный для регистрации солнечных спектров в диапазоне 0.4–23 Angstrem с временным разрешением не хуже 0.1 s. Второй инструмент представляет собой камеру-обскуру с фокусным расстоянием 58 cm. Инструмент имеет поле зрения 2×2 deg и угловое разрешение 2 arg. min, временное разрешение до 0.2 s. Энергетический диапазон определяется входным фильтром и составляет 1–10 KeV, а энергетическое разрешение – 0.5 KeV. Комбинация этих двух инструментов позволяет локализовать горячие солнечные источники в короне, определять их скорость и проводить спектральную диагностику. Ключевые слова: рентгеновская спектроскопия, солнечная корона, брэгговский спектрометр, камера-обскура.

Kozhevnikov I.F. «A special case of rolling tire vibrations» Russian journal of nonlinear dynamics (Нелинейная динамика – до 2018 г.), 15, № 1, с. 67-78 (2019)

We investigate a special case of vibrations of a loaded tire rolling at constant speed without slipping in the contact area. A previously proposed analytical model of a radial tire is considered. The surface of the tire is a flexible tread combined with elastic sidewalls. In the undeformed state, the sidewalls are represented by parts of two tori and consist of incompressible rubber described by the Mooney–Rivlin model. In the undeformed state, the tread is a circular cylinder. The tread is reinforced with inextensible cords. The tread deformations are considered taking into account the exact nonlinear conditions of inextensibility of reinforcing cords. Due to nonlinear geometric constraints in the deformed state, the tread retains its cylindrical shape, which is not circular for a typical configuration. The contact between the wheel and the ground plane occurs by a part of the tread. The previously obtained partial differential equation which describes the tire radial in-plane vibrations about the steady-state regime of rolling is investigated. Analyzing the discriminant of the quartic polynomial, which is the function of the frequency of the tenth degree and the function of the angular velocity of sixth degree, the rare case of two pairs of multiple roots is discovered. If the geometry of the tire and the internal tire pressure are known, then the angular velocity of rotation, the tire speed and the natural frequency, corresponding to this case, are determined analytically. The mode shape of vibration in the neighborhood of the singular point is determined analytically.

Leonovich A.S., Quigang Z., Kozlov D.A., Yongfu W. «Alfven waves in the magnetosphere generated by shock wave/plasmapause interaction» Солнечно-земная физика, 5, № 2, с. 11-16 (2019)

We study Alfven waves generated in the magnetosphere during the passage of an interplanetary shock wave. After shock wave passage, the oscillations with typical Alfven wave dispersion have been detected in spacecraft observations inside the magnetosphere. The most frequently observed oscillations are those with toroidal polarization; their spatial structure is described well by the field line resonance (FLR) theory. The oscillations with poloidal polarization are observed after shock wave passage as well. They cannot be generated by FLR and cannot result from instability of high-energy particle fluxes because no such fluxes were detected at that time. We discuss an alternative hypothesis suggesting that resonant Alfven waves are excited by a secondary source: a highly localized pulse of fast magnetosonic waves, which is generated in the shock wave/plasmapause contact region. The spectrum of such a source contains oscillation harmonics capable of exciting both the toroidal and poloidal resonant Alfven waves.