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21.
E. I. Kryuchkov O. K. Cheremnykh A. K. Fedorenko 《Kinematics and Physics of Celestial Bodies》2017,33(3):122-129
The properties of acoustic-gravity waves in the polar regions of the Earth’s thermosphere have been studied. It has been shown that the change in AGW amplitudes occurs against the background of large-scale rotational movements of the medium in the polar thermosphere. The amplitudes of waves increase with AGW propagation against the motion of the medium and decrease when AGW propagate along rotation. An analytical expression for the gain coefficient of AGW perturbations is obtained; the wave’s amplification effect in the opposite wind given the characteristic parameters of the thermosphere is estimated. The results are consistent with the measurements of AGW parameters in the polar regions from the “Dynamic Explorer 2” satellite.) 相似文献
22.
O. M. Lebed’ A. V. Larchenko S. V. Pil’gaev Yu. V. Fedorenko 《Geomagnetism and Aeronomy》2017,57(1):51-57
The reaction of the lower ionosphere to the solar proton events that occurred in 2011–2012 is studied in this paper based on the results of measurements of the propagation velocity and the E z /H τ ratio of the low-frequency electromagnetic pulses (atmospherics) in the ELF range at the high-latitude observatories Lovozero and Barentsburg. With numerical modeling methods, it is shown that horizontal local irregularities of the lower ionosphere conductivity profile could be a cause of the splashes in the E z /H τ ratio observed in the experiment during the solar proton event of March 7, 2012, which was a unique event in both the proton flux value and energy. 相似文献
23.
O. M. Lebed’ Yu. V. Fedorenko N. F. Blagoveshchenskaya A. V. Larchenko V. F. Grigor’ev S. V. Pil’gaev 《Geomagnetism and Aeronomy》2017,57(6):698-705
The phase velocities of TE and TEM waves at frequencies of 1017 and 3017 Hz, as well as the effect of precipitations during auroras on the velocities, are estimated in the Earth–ionosphere waveguide on the basis of observations of electromagnetic fields of an ionospheric source in experiments on modification of the lower ionosphere by a modulated high-power short-wave signals performed by the Arctic and Antarctic Research Institute (AARI) at the EISCAT/Heating test bench in October 2016. Probable electron density profiles in the plane-stratified ionosphere are retrieved from the numerical solution of a wave equation, which are used for the calculation of the phase velocities close to measured ones. 相似文献
24.
Lebed’ O. M. Fedorenko Yu. V. Manninen J. Kleimenova N. G. Nikitenko A. S. 《Geomagnetism and Aeronomy》2019,59(5):577-586
Geomagnetism and Aeronomy - A numerical model of auroral hiss propagation from the region of its generation to the ground surface is developed for the interpretation of results from ground-based... 相似文献
25.
The relationship between the directions of polar acoustic gravity waves and a wind at 250–350 km altitudes has been studied based on an analysis of the Dynamics Explorer 2 satellite measurements. A method, which makes it possible to determine the direction of these waves relative to the satellite velocity vector based on one-point measurements of different neutral atmosphere parameters, is presented. It has been established that acoustic gravity waves observed over the polar caps systematically propagate upwind, which argues for their spatial wind filtering. In the polar regions, waves mainly propagate in two directions: toward magnetic noon and 15–16 MLT. Waves tend to move counterclockwise and clockwise over the northern and southern polar caps, respectively. 相似文献
26.
E. A. Rogozhin G. N. Antonovskaya N. K. Kapustian I. V. Fedorenko 《Doklady Earth Sciences》2016,467(2):389-392
New results from seismic monitoring in the Euro-Arctic region, including the seismicity of Gakkel Ridge and the Barents–Kara Sea shelf, are presented. The data used were obtained from the Arkhan-gelsk seismic network. The role of island-based seismic stations, in particular, those in Franz Josef Land, in the monitoring network is discussed. The possibility of specifying the nature of seismicity by waveform spectral-temporal analysis, even in the case of a single station, is considered. 相似文献
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Seismic-waveform similarities for closely spaced earthquakes and explosions in particular are well established observationally. In many industrialized countries of low seismicity more than 90 per cent of seismic event recordings stem from chemical explosions and thus contribute significantly to the daily analyst workload. In this study we explore the possibility of using envelope waveforms from a priori known explosion sites (learning) for recognizing subsequent explosions from the same site excluding any analyst interference. To ensure high signal correlation while retaining good SNRs we used envelope-transformed waveforms, including both the P and Lg arrivals. To ensure good spatial resolution we used multistation (network) recordings. The interpolation and approximation neural network (IANN) of Winston (1993) was used for teaching the computer to recognize new explosion recordings from a specific site using detector output event files of waveforms only. The IANN output is a single number between 0 and 1, and on this scale an acceptance threshold of 0.4 proved appropriate. We obtained 100 per cent correct decisions between two sets of 'site explosions' and hundreds of 'non-site' explosions/earthquakes using data files from the Norwegian Seismograph Network. 相似文献
29.
Two mantle sources, two plumbing systems: tholeiitic and alkaline magmatism of the Maymecha River basin, Siberian flood volcanic province 总被引：2，自引：0，他引：2
Nicholas Arndt Catherine Chauvel Gerald Czamanske Valeri Fedorenko 《Contributions to Mineralogy and Petrology》1998,133(3):297-313
Rocks of two distinctly different magma series are found in a ∼4000-m-thick sequence of lavas and tuffs in the Maymecha River
basin which is part of the Siberian flood-volcanic province. The tholeiites are typical low-Ti continental flood basalts with remarkably restricted, petrologically evolved compositions. They have basaltic
MgO contents, moderate concentrations of incompatible trace elements, moderate fractionation of incompatible from compatible
elements, distinct negative Ta(Nb) anomalies, and Nd values of 0 to +2. The primary magmas were derived from a relatively shallow mantle source, and evolved in large crustal
magma chambers where they acquired their relatively uniform compositions and became contaminated with continental crust. An
alkaline series, in contrast, contains a wide range of rock types, from meymechite and picrite to trachytes, with a wide range of compositions
(MgO from 0.7 to 38 wt%, SiO2 from 40 to 69 wt%, Ce from 14 to 320 ppm), high concentrations of incompatible elements and extreme fractionation of incompatible
from compatible elements (Al2O3/TiO2∼1; Sm/Yb up to 11). These rocks lack Ta(Nb) anomalies and have a broad range of Nd values, from −2 to +5. The parental magmas are believed to have formed by low-degree melting at extreme mantle depths (>200 km).
They bypassed the large crustal magma chambers and ascended rapidly to the surface, a consequence, perhaps, of high volatile
contents in the primary magmas. The tholeiitic series dominates the lower part of the sequence and the alkaline series the
upper part; at the interface, the two types are interlayered. The succession thus provides evidence of a radical change in
the site of mantle melting, and the simultaneous operation of two very different crustal plumbing systems, during the evolution
of this flood-volcanic province.
Received: 6 January 1998 / Accepted: 29 June 1998 相似文献
30.
D.E. Fresnillo Fedorenko O.A. Fernández C.A. Busso O.E. Elia 《Journal of Arid Environments》1996,33(4):409-416
The phenology ofMedicago minimavar.minimaandErodium cicutariumwas studied at two different field sites in the Calden District (approx. 10 million ha), a temperate semi-arid phytogeographical region in central Argentina. One site had been protected from wild and domestic herbivores for the 6 previous years. The other adjacent site had been exposed to continuous grazing by cattle for several decades. A phenological key was made for each species in 1988, and this key was improved during the 1989 growing season when phenological observations were made every 1–3 weeks.The growth cycle ofM. minimaandE. cicutariumwas similar at the two studied sites. Initiation of the cycle occurred in autumn and appeared to be associated with soil water availability. Phenological patterns were very dynamic at the reproductive stage in both species. This stage started earlier and was faster inE. cicutariumthan inM. minima. The end of the growing season occurred during late spring, concomitant with high maximum air temperatures. Our results suggest that these species hasten their development when air temperature increases and soil water availability decreases. This could be an important strategy in these species which allows them to persist as seeds, and produce a new generation under favourable environmental conditions. 相似文献