Spatial Structure of Large-Scale Plasma Density Perturbations HF-Induced in the Ionospheric F <inf>2</inf> Region

© 2016, Springer Science+Business Media New York.We consider the experimental results obtained by studying the large-scale structure of the HF-disturbed ionospheric region. The experiments were performed using the SURA heating facility. The disturbed ionospheric region was sounded by signals radiated by GPS navigation satellite beacons as well as by signals of low-orbit satellites (radio tomography). The results of the experiments show that large-scale plasma density perturbations induced at altitudes higher than the F2 layer maximum can contribute significantly to the measured variations of the total electron density and can, with a certain arrangement of the reception points, be measured by the GPS sounding method

Spatial Structure of Large-Scale Plasma Density Perturbations HF-Induced in the Ionospheric F<inf>2</inf> Region

© 2016 Springer Science+Business Media New YorkWe consider the experimental results obtained by studying the large-scale structure of the HF-disturbed ionospheric region. The experiments were performed using the SURA heating facility. The disturbed ionospheric region was sounded by signals radiated by GPS navigation satellite beacons as well as by signals of low-orbit satellites (radio tomography). The results of the experiments show that large-scale plasma density perturbations induced at altitudes higher than the F2 layer maximum can contribute significantly to the measured variations of the total electron density and can, with a certain arrangement of the reception points, be measured by the GPS sounding method

The solution of wear-contact problems by means of electrical simulation

В статті розглянуто сутність електростатичної аналогії між рівняннями електростатики та теорії пружності. На основі цієї аналогії запропоновано спосіб вирішення задачі щодо контакту двох пружних тіл з врахуванням зносу за допомогою електричного моделювання з використанням квазістаціонарного електричного поля. Вирішена зносоконтактна задача щодо убчастого зачеплення. Отримано площадки контакту для різних варіантів контактування зубів з початковим точковим контактом. Досліджено вплив зносу контактуючих поверхонь на розподілення контактного тиску. Побудовані епюри контактного тиску по різним січенням площадок контакту.Purpose. A great number of works in the field of contact interaction mechanics including those with account of the wear of contact surfaces, and the desire to take into consideration the factors even at the stage of designing elements of higher kinematic pairs proves the topicality of the problem under consideration. However, solving such problems by means of analytical and numeric methods is connected with the necessity to overcome considerable difficulties, and in some cases it is impossible. That is why other methods of solving them, and, in particular, with help of electrical simulation are of both scientific and practical interest. Design/methodology/approach. The paper considers the essence of electrostatic analogy. It presents the way of solving 3D contact problems by means of electrical simulation based on the application of quasi-stationary electric field. It also presents the description of a special electrical simulation device made for solving the problems. The device enables to do experimental research and process obtained results automatically. It is shown that the accuracy of the results obtained in the experiments is enough for engineering applications. Findings. The paper also presents the problem about point contact of gear teeth with account of wear. It shows the influence of contact surfaces wear on the distribution of contact pressures. It presents contact areas for different points of gearing. The diagrams of contact pressures on their different sections are given. Originality/value. It is concluded that the solution of wear-contact problems enables to choose the best geometry of contact surfaces of elements of higher kinematic pairs on the designing stage and get a considerable economic effect.В статье рассмотрена сущность электростатической аналогии между уравнениями электростатики и теории упругости. На основе этой аналогии предложен способ решения задачи о контакте двух упругих тел с учетом износа с помощью электрического моделирования с использованием квазистационарного электрического поля. Решена износоконтактная задача применительно к зубчатому зацеплению. Получены площадки контакта для различных вариантов контактирования зубьев с первоначально точечным контактом. Исследовано влияние износа контактирующих поверхностей на распределение контактных давлений. Построены эпюры контактных давлений по различным сечениям площадок контакта

Anomalous attenuation of extraordinary waves in the ionosphere heating experiments

Multiple scattering of radio waves by artificial random irregularities HF-induced in the ionosphere F region may cause significant attenuation of both ordinary and extraordinary waves together with common anomalous absorption of ordinary waves due to their non-linear conversion into plasma waves. To demonstrate existence and strength of this effect, direct measurements of attenuation of both powerful pump wave and weak probing waves of extraordinary polarization have been carried out during an experimental campaign on September 6, 7 and 9, 1999 at the Sura heating facility. The attenuation magnitude of extraordinary waves reaches of 1-10 dB over a background attenuation caused by natural irregularities. It is interpreted in the paper on the base of the theory of multiple scattering from the artificial random irregularities with characteristic scale lengths of 0.1-1 km. Simple procedure for determining of irregularity spectrum parameters from the measured attenuation of extraordinary waves has been implemented and some conclusions about the artificial irregularity formation have been obtained.Comment: 17 pages, 9 figure

Simultaneous observations of the 557.7 nm airglow and stimulated electromagnetic emission during HF pumping of the ionosphere with diagnostic schedule: First results

The first results on simultaneous observation for artificial airglow emission at 557.7 nm (green line) and stimulated electromagnetic emission (SEE) during HF pumping of the ionosphere with specially designed HF pulsing sequence are reported. Ionospheric radio pumping was performed at the "Sura" radio facility situated near Niznhny Novgord, Russia. The measurements of airglow were handled at the Astronomical Observatory of Kazan State University (220 km to the east of "Sura" facility) by the astronomical telescope AZT-14 connected with the electric photometer. During several "Sura" runs enhancements of the airglow intensity in time with pump wave pulses were observed after the pump wave switch from continuous transmission to low duty cycle pulse transmission. The airglow and SEE intensities and SEE decay rates were correlated. © 2004 COSPAR. Published by Elsevier Ltd. All rights reserved

Studies of artificial airglow emission at 557.7 nm (green line) of upper atmosphere caused by "Sura" facility

Some experimental results of artificial airglow emission at 557.7 nm (green line) during HF pumping of the ionosphere with specially designed HF pulsing sequence are reported. Ionospheric radio pumping was performed at the "Sura" radio facility situated near Niznhny Novgord, Russia. The measurements of airglow were handled at the Astronomical Observatory of Kazan State University (220 km to the east of "Sura" facility) by the astronomical telescope AZT-14 connected with the electric photometer. During several "Sura" runs enhancements of the airglow intensity in time with pump wave pulses were observed after the pump wave switch from continuous transmission to low duty cycle pulse transmission

Homogeneity and plane-wave limits

We explore the plane-wave limit of homogeneous spacetimes. For plane-wave limits along homogeneous geodesics the limit is known to be homogeneous and we exhibit the limiting metric in terms of Lie algebraic data. This simplifies many calculations and we illustrate this with several examples. We also investigate the behaviour of (reductive) homogeneous structures under the plane-wave limit.Comment: In memory of Stanley Hobert, 33 pages. Minor corrections and some simplification of Section 4.3.

Generation of Artificial Ionospheric Irregularities in the Midlatitude Ionosphere Modified by High-Power High-Frequency X-Mode Radio Waves

© 2014, Springer Science+Business Media New York. We consider the properties of the artificial ionospheric irregularities excited in the ionospheric F2 region modified by high-power high-frequency X-mode radio waves. It is shown that small-scale (decameter) irregularities are not generated in the midlatitude ionosphere. The intensity of irregularities with the scales l⊥≈50 m to 3 km is severalfold weaker compared with the case where the irregularities are excited by high-power O-mode radio waves. The intensity of the larger-scale irregularities is even stronger attenuated. It is found that the generation of large-scale (l⊥ ≈5–10 km) artificial ionospheric irregularities is enhanced at the edge of the directivity pattern of a beam of high-power radio waves

Gyroharmonic features of the hf-induced ionospheric irregularities

Gyroharmonic features of the different-scale artificial plasma-density irregularities excited by HF modification of the ionospheric F2 region under conditions where the frequency of the O-mode pump wave is close to the fourth gyroharmonic frequency of electrons in the pump wave - plasma interaction region are considered. © 2012 Springer Science+Business Media New York