Cотрудники института
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Cотрудники института
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Шапошников Владимир Евгеньевич Образование:
Область научных интересов: Профессиональная карьера: Научные визиты в разные страны, наиболее длительные и многократные визиты в Институт космических исследований Австрийской академии наук (Австрия). Членство в профессиональных организациях: Награды, премии, гранты: Педагогическая деятельность: Публикации: Наиболее значительные работы и результаты: 1. “Перенос поляризованного излучения в магнитоактивной плазме” (совместно с В.В. Железняковым и Е.В. Суворовым) Астрономический ж., Т. 51, В. 2, 1974. Выведены уравнения переноса поляризованного излучения в магнитоактивной плазме произвольной анизотропией и любой степенью неортогональности нормальных волн. Показана идентичность уравнений переноса для тензоров поляризации, выраженных через электрическую индукцию и напряженность электрического плоя. Для слабоанизотропных сред получено решение уравнений переноса поляризованного излучения. На основе выведенных уравнений выяснены пределы применимости и взаимное соответствие разных форм уравнений переноса поляризации. 2. “О магнитодрейфовом излучении на продольных волнах в магнитосфере нейтронной звезды” Астрофизика, Т. 17, в 4, p.749-763, 1981. Рассмотрен магнитодрейфовый механизм генерации продольных волн, обусловленный движением релятивистских частиц вдоль искривленных силовых линий магнитного поля. Показано, что эффективное усиление волн возможно при распространении продольных волн как в нерелятивистской, так и в релятивистской плазме. Проведена оценка оптической толщины для магнитодрейфового поглощения в условиях, характерных для магнитосферы пульсара. Определены уровни энергии релятивистского электрона, движущегося вдоль искривленных силовых линий магнитного поля. 3. The origin of s-bursts in Jupiter's decametric radio spectra (with V. V. Zaitsev and E.Ya.Zlotnik). Astron.Astrophys., V.169, No. 1-2, P. 345-354, 1986. A model for Io phase dependent S-bursts in Jupiter's decametric radio emission is proposed. The source region is a multi-component system composed of an equilibrium plasma and an admixture of loss-cone ions and electrons. The system is localized in the Jovian ionosphere at the foot of the Io flux tube, in the region of a strong (ωB >> ωp) quasi-homogeneous magnetic field. Different types of conversion of plasma waves into electromagnetic waves lead to quasi-periodic trains of S-bursts and isolated simple S-bursts. The negative frequency drift is due to the group delay of extraordinary waves during their propagation in the region with low refractive index (ne << 1). The strong beaming explains the Io phase dependent S-bursts. The central meridian longitude phase control is due to the fact that Io traverses periodically the region of increased plasma density (plasma torus) and that the number of particles reaching the source increases. 4. “On elliptical polarization of the decametric radio emission and the linear mode coupling in the Jovian magnetosphere” (with Kocharovsky, Vl. V.; Kocharovsky, V. V.; Ladreiter, H. P.; Rucker, H. O.; Zaitsev V. V) Astronomy and Astrophysics, v.326, p.386-395, 1997. We consider the origin of the elliptical polarization of Jupiter's decametric emission as a consequence of the moderate linear mode coupling which takes place in the Jovian magnetosphere outside of the source region. We recognize conditions of emission propagation along the ray path which are necessary for forming of the observed polarization characteristic and show that our model explains the main observed properties of the polarization (value of ellipticity, independence of polarization on frequency and time, stability of polarization from storm to storm), does not need low plasma densities in the emission source and does not contradict the modern knowledge on the decametric emission origin. We show that there is no strong correlation between polarization of the emission at the source and the observed polarization. The observed degrees of (linear and circular) polarization have to be assumed as limits of possible degrees of the polarization of the emission escaping the source region. The value of the ellipticity is defined by the level of the magnetospheric plasma density ne in the "transitional region", that is in a part of the ray path where the polarization of the normal waves is essentially elliptical. The plasma density in this region is quite low ne<0.4 cm-3 and is related to the local electron gyrofrequency as ne ∞ (fBe)ν where ν=~1/1.8. 5. “Ускорение электронов в ионосфере Ио” (совместно с Зайцевым В.В. и Рукером Х.О.) Астрономический журнал, 2003, том 80, №8, с. 761–768. Рассмотрен механизм ускорения электронов в ионосфере Ио, обусловленный движением спутника в магнитном поле Юпитера и наличием у Ио собственной ионосферы. Обращено внимание на важную роль анизотропии проводимости ионосферы, приводящей к появлению продольной по отношению к магнитному полю планеты компоненты электрического поля разделения зарядов. Анизотропия проводимости приводит к тому, что электрическое полеEi, индуцированное благодаря движению Ио, вызывает в ионосфере Ио не только педерсеновский электрический ток вдоль Ei, но стремится также генерировать холловский ток, направление которого в «лобовой» и «хвостовой» частях ионосферы Ио приблизительно ортогонально к поверхности спутника. Этот ток, однако, не может замкнуться на поверхность, в результате чего в ионосфере Ио возникает мощное поле разделения зарядов, имеющее проекцию на направление магнитного поля, и величину, сравнимую с величиной индуцированного электрического поля. В работе также рассмотрено «убегание» электронов вдоль магнитного поля и дана интерпретация появления «активных долгот» и преимущественного расположения источников декаметрового радиоизлучения Юпитера в северном полушарии. Приведена оценка характерных энергий и потоков ускоренных электронов, инжектируемых в магнитную трубку Ио (МТИ). Показано, что энергии в этих электронных потоках достаточно, чтобы обеспечить наблюдаемое из МТИ электромагнитное излучение. 6. “Dependence of the Io-related decametric radio emission of Jupiter on the central meridian longitude and Io's "active" longitudes” (with V. V. Zaitsev and H. O. Rucker) Astronomy and Astrophysics, Volume 454, Issue 2, August I 2006, pp.669-676, 2006 The statistical analysis of the Io-related decametric radio emission of Jupiter shows that this emission depends precisely on the central meridian longitude. This dependence is the result of the existence of Io's "active" longitudes, i.e. particular regions of Io's orbit, which are fixed with respect to the Jovian magnetic field and at which Io-related emission occurs more often. The paper considers the mechanism of the formation of Io's "active" longitudes. The formation of Io's "active" longitudes is caused by two factors: first, the change of the efficiency of particle acceleration in Io's ionosphere, depending on Io's longitude, and second, the degree of broadening of the angular spectrum of accelerated electrons during their passing through the plasma torus. It is shown that the mechanism considered explains rather well why Io-related decametric bursts begin to appear much more often in longitudes of the range 120° ≤ λIo ≤ 300° (λIo is the longitude in the frame III), and why one predominantly observes the emission from the sources located in the northern Jovian hemisphere. 7. “Аcceleration of Electrons in Titan’s Ionosphere” (with V.V. Zaitsev, M.L. Khodachenko, H.O. Rucker, M. Panchenko,), 2010, Journal of Geophysical Research,, Volume 115, A03212, doi: 10.1029/2010JA016041 A consideration of the acceleration mechanism which supplies the fast electrons to the source of Saturnian kilometric radiation (SKR) and an interpretation of the recently reported observational indications of the influence of Titan on the SKR are presented. The proposed mechanism operates by the effect of the different magnetization of the electrons and ions in Titan's ionosphere which in the course of Titan's motion through the Saturnian magnetic field causes the creation of a charge-separation electric field. This field has a component parallel to the magnetic field and accelerates part of the ionospheric electrons (called “runaway electrons”). The performed estimates show that the mechanism accelerates the runaway electrons up to an energy of 5 keV. The power of the acceleration mechanism is sufficient for SKR generation and also for the ultraviolet luminescence of Titan's atmosphere. The weakening of the SKR when Titan passes on the dayside of Saturn is due to a decrease of the magnetic field strength near the dayside magnetopause, when the Moon escapes the Saturnian magnetosphere, as well as due to the break in the magnetic connection between the electron acceleration region on Titan and the SKR sources. The latter prevents the penetration of the accelerated electrons into the radiation generation region. When Titan is on the nightside of Saturn, it enters into shell L=14, which is stretched owing to the ring current. In this case, the electrons that accelerated in the ionosphere of Titan can reach the nightside SKR sources and activate them and therefore being the reason for the Titan influence on the SKR. 8. “Parametric mechanism for the formation of Jovian millisecond bursts” (with Korobkov, S. V.; Rucker, H. O.; Kostrov, A.V.,Guschin, M.E., Litvinenko, G. V.) Journal of Geophysical Research: Space Physics, Volume 116, Issue A3, CiteID A03205, doi: 10.1002/jgra.50360, 2011. We develop a theory of formation of a fine structure in the dynamic spectra of the Jovian decametric radio emission. Main attention is paid to the formation of narrowband (NB) emission and quasiperiodic trains of short (S) bursts. Our model is based on the effects of occurrence of the amplitude-frequency modulation and extension of the frequency spectrum of a signal during propagation of radiation in a medium with time-varied parameters. It is shown that nonstationary disturbances of the planetary magnetic field and strong frequency dispersion of the plasma at frequencies close to the cutoff frequency of the extraordinary wave in the Jovian ionosphere play a crucial role in the formation of NB emission and quasiperiodic trains of S bursts. As a result of the numerical experiments, it was concluded that the amplitude-frequency characteristics of an initially continuous signal can drastically vary as a functions of the form of the magnetic field disturbance in the Jovian ionosphere. Structures similar to those observed in the real experiments, ranging from NB emission and quasiperiodic trains of S bursts to more complex structures, arise in the dynamic spectrum. Time variation in the conditions of generation and propagation of decametric radiation in the Jovian ionosphere is reflected in the dynamic spectrum as a time variation in the fine structure of the radiation. For example, a structure of the NB emission type is replaced by a quasiperiodic train of S bursts and vice versa. 9. “On ultraviolet emission observed on the flanks of Io” (with Zaitsev, V. V.; Rucker, H. O.; Litvinenko, G. V.) Volume 118, p. 4248-4252, doi: 10.1002/jgra.50360, 2013. Two very bright ultraviolet (UV) radiation sources (equatorial spots) which are located on the limb of Io near its equator have been detected in a series of observations with the Hubble space telescope. In this paper, we propose the mechanism that provides the sufficient energy of the equatorial spots to explain their high brightness in the UV wavelength range, According to the proposed model, this UV radiation is generated due to electrons which are formed as a result of additional ionization of the atmosphere in the front part of the satellite. These secondary electrons in crossed electric and magnetic fields are shifted downstream into Io’s flanks. The optical depth of the source increases on the flanks of Io’s atmosphere (from the vantage point of the observer), and we therefore observe the brightest UV radiation in this region, the value of which is in good agreement with the measured values. Also, a reasonable explanation is given for the main observed properties of the UV equatorial spots, such as (1) a correlation between the brightness of the emission and the magnetic longitude of Io and as a result Io’s distance from the plasma torus centrifugal equator; (2) a correlation between the equatorial spot location and the planetary magnetic field orien19
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