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Отраслевые подборки (УДК)
  1. Отраслевые подборки (УДК)
  2. Математика. Естественные науки
Издания подборки 151 - 160 из 191
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151.
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Авторы:
Baishev Dmitriy G., Barkova Elena S., Solovyev Stepan I., Yumoto Kiyohumi, Engebretson Mark, Koustov A. V.
Заглавие: Formation of large-scale, "giant" undulations at the equatorial boundary of diffuse aurora and Pc5 magnetic pulsations during the January 14, 1999 magnetic storm

Количество страниц: 4 с.

In the present study we investigate the undulations at the equatorial boundary of diffuse aurora and their relationship to the development of magnetic and auroral substorms and excitation of Pc5 magnetic pulsation on January 14, 1999. The observed undulations had wave-length of ~200-300 km and amplitude of ~50-250 km and they propagated westward with the velocity of ~0,7 km/s. It is found that the undulations began ~40 min after the substorm onset and lasted for ~80 min, all the way to the end of the substorm. During both active and recovery phases of the substorm the undulations were accompanied by the enhancement of the DP2 equivalent current system and by the formation of WTS. Concurrently with undulations, there were observed Pc5 magnetic pulsations of an oscillation period roughly equal to the ratio of the undulation wavelength to their propagation velocity. Observations are interpreted in terms of the shear/ballooning instability excitation near the plasmapause and subsequent generation of drift hydromagnetic waves.

Formation of large-scale, "giant" undulations at the equatorial boundary of diffuse aurora and Pc5 magnetic pulsations during the January 14, 1999 magnetic storm / D. G. Baishev, E. S. Barkova, S. I. Solovyev, K. Yumoto, M. J. Engebretson and A. V. Koustov // Proceedings of the Fifth International Conference on Substorms : 16-20 May 2000 Congress Centre of the Arctic and Antarctic Research Institute, St. Petersburg, Russia. − Noordwijk, Netherlands : European Space Agency, 2000. − P. 427-430.

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152.
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Автор:
Boroyev Roman Nikolaevich
Заглавие: Dynamics of the field-aligned current during substorms with a sharp onset of the expansion phase

Количество страниц: 4 с.

By using satellite magnetic field measurements it is shown that before the substorm expansion phase onset the field-aligned currents of zone 2 type are not always observed on the geosynchronous orbits at the midnight sector. The relationship between the appearance of the field-aligned currents of zone 2 types before the beginning of the substorm expansion phase and the active phase duration and the preceding magnetic disturbance level has been found. It is found that if the expansion phase lasts less than 11 min, the appearance probability of the field-aligned current of zone 2 type before the substorm expansion phase onset T0 decreases. As the geomagnetic activity rises before a substorm, the probability of the beginning of the field-aligned currents before T0 increases. These results indicate that substorms in which the field-aligned currents of zone 2 type the T0 onset are absent, can be probably developed in the distant part of the magnetotail.

Boroyev, R. N. Dynamics of the field-aligned current during substorms with a sharp onset of the expansion phase / R. N. Boroyev // Proceedings of the Fifth International Conference on Substorms : 16-20 May 2000 Congress Centre of the Arctic and Antarctic Research Institute, St. Petersburg, Russia. − Noordwijk, Netherlands : European Space Agency, 2000. − P. 377-380.

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153.
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Авторы:
Boroyev Roman Nikolaevich, Velichko Vitaly Andreevich, Baishev Dmitriy Gavrilievich
Заглавие: Local increase of field-aligned current intensity before a substorm onset

Количество страниц: 4 с.

By using data treatment results of mid-latitude geomagnetic variations, the significant increase of the local current system intensity with the eastern direction current system, arising near the meridian of expected substorm center ~10-30 min before the break-up onset, has been found. A comparison of longitudinal sizes of two current system, forming the substorm disturbance before and after the onset of the substorm expansion phase, has been carried out. The longitudinal size of the current loop of the substorm growth phase is nearly twice as small as azimuth scale of the substorm current wedge, and the current strength is as week as 2.7-12 times.

Boroyev, R. N. Local increase of field-aligned current intensity before a substorm onset / R. N. Boroyev, V. A. Velichko, D. G. Baishev // Proceedings of the Fifth International Conference on Substorms : 16-20 May 2000 Congress Centre of the Arctic and Antarctic Research Institute, St. Petersburg, Russia. − Noordwijk, Netherlands : European Space Agency, 2000. − P. 279-282.

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154.
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Авторы:
Boroyev Roman Nikolaevich, Gelberg Mikhail Germanovich
Заглавие: Dependence of longitudinal localization of substorm center on geosynchronous orbits on the IMF Bγ-component

Количество страниц: 4 с.

The dependence of the longitudinal substorm center localisation on geosynchronous orbits on the IMF Bγ-component has been studied. It is shown that the local magnetic time of the longitudinal substorm center localisation in the magnetosphere varies from evening hours to morning hours as the Bγ-component increases. At low solar wind speeds the substorm centers localize nearer to the evening sector. The ionospheric projection of the substorm center magnetospheric localisation shifts westward at By0. Maximum longitudinal shifts of substorm centers in the ionosphere relative to their location in the magnetosphere are - 3.5 h at Bγ=-4 nT and 3.5 h at Bγ=4.4 nT. Thus, the change of the substorm center localisation relative to the midnight in the ionosphere is caused by both the change of the substorm center position in the magnetosphere and a turn of the magnetotail relative to X-axis.

Boroyev, R. N. Dependence of longitudinal localization of substorm center on geosynchronous orbits on the IMF Bγ-component / R. N. Boroyev, M. G. Gelberg // Proceedings of the Fifth International Conference on Substorms : 16-20 May 2000 Congress Centre of the Arctic and Antarctic Research Institute, St. Petersburg, Russia. − Noordwijk, Netherlands : European Space Agency, 2000. − P. 41-44.

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155.
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Автор:
Gavrilyeva Galina Alekseevna
Заглавие: Measurements of the mesosphere temperature by two molecular emissions in Yakutsk (62°N, 129,5°E)

Количество страниц: 4 с.

The results of the hydroxyl and oxygen molecules rotational temperature measurements during two observational seasons 1999-2001 at Maymaga station (φ=63°N;λ=129.50°E) are presented. The rotational temperatures of OH(6,2) and O2 (0,1) bands have been measured with the infrared spectrograph equipped by the cooled CCD registration system. It is shown that the amplitude of seasonal change of hydroxyl rotational temperature is greater than the molecular oxygen variation. OH temperatures have been systematically higher the O2 ones during winter. An abrupt decrease of the O2 intensity connected with the springtime transition of the atmospheric circulation is found in both time series. For the first time a change of the temperature vertical gradient sign caused by mesopause height displacemet to a higher (winter) level was shown in the data of August-September 2001.

Gavrilyeva, G. A. Measurements of the mesosphere temperature by two molecular emissions in Yakutsk (62°N, 129,5°E) / G. A. Gavrilyeva // Physics of auroral phenomena : proceedings of the 26th annual seminar, 25 - 28 February 2003. – 2003. – P. 198-201.

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156.
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Авторы:
Ammosov Petr Petrovich, Gavrilyeva Galina Alekseevna
Заглавие: Observations of short-term waves with an all sky camera in the infrared oh brightness over Yakutsk

Количество страниц: 3 с.

Statistical analysis of internal gravity wave parameters registered by variations of the hydroxyl molecule emission is presented. The wave structures are detected with an all sky infrared camera at the optical station of Maimaga (φ=63° N; λ=129.50°E geographic). The data obtained for the period of 1998 to 2002 show that the small-scale internal gravity waves propagate predominantly westward. The observed wavelengths vary from 15.4 to 100 km. (the average value is ~40 km), the horizontal phase speeds are between 19 and 166 m s-¹ (the average value is ~63 m s-¹) and the estimated periods are 9-90 min (the average value is ~17 min). The wavelengths and phase speeds at high latitudes is probably due to the large intensities of the filtering winds compared to those in the middle atmosphere. The short waves (wavelengths shorter than 17.5 km) propagate in the same direction as the long ones.

Ammosov, P. P. Observations of short-term waves with an all sky camera in the infrared oh brightness over Yakutsk / P. P. Ammosov, G. A. Gavrilyeva // Physics of auroral phenomena : proceedings of the 26th annual seminar, 25 -28 February 2003. – 2003. – P. 179-181.

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157.
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Авторы:
Skryabin Nikolay Georgievich, Samsonov Sergey Nikolaevich, Plotnikov Igor Yakovlevich
Заглавие: Influence of a change in solar magnetic field polarity on the Jovian electron flux intensity

Количество страниц: 3 с.

The Jupiter is a powerful regular source of high-energy electrons (0,2-40 MeV). In this connection their density in the near-Earth space systematically increases with a period of 399 days, which is coincident with the synodic period of Jupiter. According to our estimations, their energy is sufficient to produce a significant local reduction of the magnetic field in the IMF sector connected with the Jupiter. In this paper the evidence is presented that the electron fluxes in the Jovian sector are controlled by the general magnetic field of the Sun. A treatment of 399-day intervals of the electron fluxes and IMF, obtained from spacecraft data for the period of 1963 to 2000 has been performed by superposed epoch technique taking into account the periodic change of the solar magnetic field polarity. Having adopted the Jupiter opposition day to be an epoch zero, the changes in particle intensity and IMF components under different signs of the general magnetic field of the Sun are found by using a large dataset (9925 days). The times of 399-day variation maxima in different periods of solar activity are compared and a character of their displacement relative to Jupiter opposition momentsis discussed.

Skryabin, N. G. Influence of a change in solar magnetic field polarity on the Jovian electron flux intensity / N. G. Skryabin, S. N. Samsonov, I. Ya. Plotnikov // Physics of auroral phenomena : proceedings of the 26th annual seminar, 25 - 28 February 2003. – 2003. – P. 159-161.

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158.
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Авторы:
Sokolov Vasiliy Dmitrievich, Samsonov Sergey Nikolaevich
Заглавие: The dynamics of auroral absorption parameters in the 22nd solar activity cycle

Количество страниц: 3 с.

Examination of auroral absorption (AA) occurrence rate and AA meridional distribution versus local time and in the course of the solar cycle has been performed by riometer observations from 1985 to 1995 at the longitude of Yakutsk. Geomagnetic latitude of the region of absorption maximum occurrence changes in the course of the solar cycle from 66.5° to 64.4°. The largest displacement of this region to lower latitudes is observed during years of maximum solar activity. The half-width of the region is ~8° at solar minimum and ~10° at solar maximum. It has been also revealed that the region of AA is shifted to higher latitudes at daytime (1000-1400LT), and to lower ones in the evening (1800-2000LT), the displacement from the daily average position being ~1° and ~3° in the years of solar activity maximum and minimum, respectively. In all years at 2000-2100LT a short-term extension of the AA region by 1-4° is observed. The interpretation of the observationa is proposed.

Sokolov, V. D. The dynamics of auroral absorption parameters in the 22nd solar activity cycle / V. D. Sokolov, S. N. Samsonov // Physics of auroral phenomena : proceedings of the 26th annual seminar, 25 - 28 February 2003. – 2003. – P. 95-97.

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159.
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Авторы:
Sokolov Vasiliy Dmitrievich, Danilov A. A., Samsonov Sergey Nikolaevich
Заглавие: Dependence of semi-diurnal variation of auroral absorption on a geomagnetic disturbance

Количество страниц: 4 с.

From data of riometer observations from 1986 to 1993 at stations of Kotelny Island, Tixie Bay and Zhigansk the semi-diurnal variations of occurrence frequency of auroral absorption and their dependence on geomagnetic activity have been determined. It has been found that the phase of semi-diurnal variation maximum is systematically shifted to earlier hours with the rise of geomagnetic disturbance. The reason of this experimental fact is discussed.

Sokolov, V. D. Dependence of semi-diurnal variation of auroral absorption on a geomagnetic disturbance / V. D. Sokolov, A. A. Danilov, S. N. Samsonov // Physics of auroral phenomena : proceedings of the 26th annual seminar, 25 - 28 February 2003. – 2003. – P. 91-94.

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160.
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Авторы:
Velichko Vitaly Andreevich, Boroyev Roman Nikolaevich, Plotnikov Igor Yakovlevich, Baishev Dmitriy Gavrilievich
Заглавие: Effect of Bγ IMF in substorm current wedge formation

Количество страниц: 4 с.

Based on the data of longitudinal chain of midlatitude stations in the northern hemisphere, substorm-associated field-alighned currents (FACs) are examined. A comparison of IMF component variations with surface FAC characteristics in substorm sites is performed. It is shown that the ratio between the upward and downward surface FAC intensities depends on By IMF. In this regard, the conditions are discussed that favor currents flowing from the dayside cusp to nightside auroral region. These currents, which position is dependent on By IMF direction, can be responsible for difference between the upward and downward current-wedge-associated FACs.

Effect of Bγ IMF in substorm current wedge formation / V. A. Velichko, R. N. Boroev, I. Ya. Plotnikov, D. G. Baishev // Physics of auroral phenomena : proceedings of the 26th annual seminar, 25 - 28 February 2003. – 2003. – P. 45-48.

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