Investigation of the Earth Ionosphere using the Radio Emission of Pulsars

The investigation of the Earth ionosphere both in a quiet and a disturbed states is still desirable. Despite recent progress in its modeling and in estimating the electron concentration along the line of sight by GPS signals, the impact of the disturbed ionosphere and magnetic field on the wave propagation still remains not sufficiently understood. This is due to lack of information on the polarization of GPS signals, and due to poorly conditioned models of the ionosphere at high altitudes and strong perturbations. In this article we consider a possibility of using the data of pulsar radio emission, along with the traditional GPS system data, for the vertical and oblique sounding of the ionosphere. This approach also allows to monitor parameters of the propagation medium, such as the dispersion measure and the rotation measure using changes of the polarization between pulses. By using a selected pulsar constellation it is possible to increase the number of directions in which parameters of the ionosphere and the magnetic field can be estimated.Comment: 13 pages, 4 figures, Baltic Astronomy, vol.22, 53-65, 201

АНИЗОТРОПНЫЕ СВОЙСТВА ВЕРХНЕЙ МАНТИИ ЦЕНТРАЛЬНОЙ АЗИИ ПО ДАННЫМ ДИСПЕРСИИ ГРУППОВЫХ СКОРОСТЕЙ ВОЛН РЭЛЕЯ И ЛЯВА

The article presents the results of the study focused on the anisotropic properties of the upper mantle in Central Asia. The study is based on a representative set of the group velocity dispersion curves for Rayleigh and Love waves. The dispersion curves were calculated in the range of 10–250 s. The maps of group velocity distribution pat‐ terns and the horizontal resolution estimates were calculated by the surface‐wave tomography method developed for a spherical surface. Based on the maps, the local group velocity dispersion curves were reconstructed for the given points within the study region, which were then converted into the one‐dimensional velocity sections of SV‐ and SH‐waves, and a vertical anisotropy coefficient was estimated. A three‐dimensional anisotropic model shows the ve‐ locity distribution pattern of S‐waves in the crust and the mantle to the depth of 500 km. According to this model, ver‐ tical anisotropy in the upper mantle is observed to the depth of about 250 km and has maximum values in the depth interval from the crustal bottom to 150 km. The anisotropic properties are unevenly distributed and reflect the geo‐ logical structure of the study area. Therefore, tectonically active regions are characterized by the high values of the anisotropy coefficient and the reduced values of the S‐wave velocities. The presented results can contribute to the further development of more detailed and strictly proved geodynamic models of the study area.В работе представлены результаты исследования анизотропных свойств верхней мантии Цен‐ тральной Азии, выполненного на основании представительной выборки дисперсионных кривых групповых скоростей основной моды волн Рэлея и Лява. Дисперсионные кривые рассчитывались в диапазоне периодов 10–250 с. Карты распределений групповых скоростей с оценками горизонтального разрешения вычислялись методом поверхностно‐волновой томографии для сферической поверхности. По результатам картирования в заданных с учетом разрешения точках области исследования восстанавливались локальные дисперсионные кривые групповых скоростей и проводилась их инверсия в одномерные скоростные разрезы волн SV и SH и оценивался коэффициент вертикальной анизотропии. Таким образом, была получена трехмерная анизо‐ тропная модель распределения скоростей волн S в коре и мантии до глубины 500 км. Показано, что верти‐ кальная анизотропия в верхней мантии наблюдается до глубины около 250 км, с максимумом в интервале глубин от подошвы коры до 150 км. Распределение анизотропных свойств является неоднородным и отра‐ жает геологическое строение исследуемой области. Так, тектонически активные регионы характеризуются высокими значениями коэффициента анизотропии и пониженными значениями скоростей S‐волн. Получен‐ ные результаты в дальнейшем могут способствовать построению более детальных и обоснованных геодина‐ мических моделей рассматриваемой территории

ГЕОДИНАМИЧЕСКАЯ АКТИВНОСТЬ НОВЕЙШИХ СТРУКТУР И ПОЛЯ ТЕКТОНИЧЕСКИХ НАПРЯЖЕНИЙ СЕВЕРО-ВОСТОКА АЗИИ

Based on the analysis of changes in the stress-strain state of the crust at the boundary of the Eurasian and North American tectonic plates, we develop a dynamic model of the main seismogenerating structures inNortheast Asia. We have established a regularity in changes of geodynamic regimes within the interplate boundary between the Kolyma-Chukotka crustal plate and the Eurasian, North American and Pacific tectonic plates: spreading in the Gakkel Ridge area; rifting in the Laptev Sea shelf; a mixture of tectonic stress types in the Kharaulakh segment; transpression in the Chersky seismotectonic zone, in the segment from the Komandor to the Aleutian Islands, and in the Koryak segment; and crustal stretching in the Chukotka segment.Анализ изменений напряженно-деформированного состояния земной коры, проведенный вдоль границы Евразийской и Североамериканской литосферных плит, позволил обосновать динамическую модель главных сейсмогенерирующих структур территории северо-востока Азии. В пределах единой межплитной границы, отделяющей Колымо-Чукотскую коровую плиту от Евразийской, Североамериканской и Тихоокеанской литосферных плит, наблюдается закономерная смена геодинамических режимов: спрединг хребта Гаккеля; рифтогенез на шельфе моря Лаптевых; смешанное поле тектонических напряжений в Хараулахском сегменте; транспрессия в сейсмотектонической зоне Черского, на участке от Командорских до Алеутских островов и в Корякском сегменте; растяжение в Чукотском сегменте

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ANISOTROPIC PROPERTIES OF THE UPPER MANTLE IN CENTRAL ASIA ACCORDING TO THE GROUP VELOCITY DISPERSION CURVES FOR RAYLEIGH AND LOVE WAVES

The article presents the results of the study focused on the anisotropic properties of the upper mantle in Central Asia. The study is based on a representative set of the group velocity dispersion curves for Rayleigh and Love waves. The dispersion curves were calculated in the range of 10–250 s. The maps of group velocity distribution pat‐ terns and the horizontal resolution estimates were calculated by the surface‐wave tomography method developed for a spherical surface. Based on the maps, the local group velocity dispersion curves were reconstructed for the given points within the study region, which were then converted into the one‐dimensional velocity sections of SV‐ and SH‐waves, and a vertical anisotropy coefficient was estimated. A three‐dimensional anisotropic model shows the ve‐ locity distribution pattern of S‐waves in the crust and the mantle to the depth of 500 km. According to this model, ver‐ tical anisotropy in the upper mantle is observed to the depth of about 250 km and has maximum values in the depth interval from the crustal bottom to 150 km. The anisotropic properties are unevenly distributed and reflect the geo‐ logical structure of the study area. Therefore, tectonically active regions are characterized by the high values of the anisotropy coefficient and the reduced values of the S‐wave velocities. The presented results can contribute to the further development of more detailed and strictly proved geodynamic models of the study area

Investigation of the Earth Ionosphere Using the Radio Emission of Pulsars

The investigation of the Earth ionosphere both in a quiet and a disturbed states is still desirable. Despite recent progress in its modeling and in estimating the electron concentration along the line of sight by GPS signals, the impact of the disturbed ionosphere and magnetic field on the wave propagation still remains not sufficiently understood. This is due to lack of information on the polarization of GPS signals, and due to poorly conditioned models of the ionosphere at high altitudes and strong perturbations. In this article we consider a possibility of using the data of pulsar radio emission, along with the traditional GPS system data, for the vertical and oblique sounding of the ionosphere. This approach also allows to monitor parameters of the propagation medium, such as the dispersion measure and the rotation measure using changes of the polarization between pulses. By using a selected pulsar constellation it is possible to increase the number of directions in which parameters of the ionosphere and the magnetic field can be estimated