共查询到20条相似文献,搜索用时 15 毫秒
1.
I. Yu. Sergeev V. M. Sorokin A. K. Yashchenko 《Radiophysics and Quantum Electronics》2000,43(8):619-625
We consider the radiation of low-frequency electromagnetic waves from an axisymmetric current and propagation of these waves in a homogeneous ionospheric plasma with Hall and Pedersen conductivities. We obtain an analytical expressions for the fields excited by pulsed radial and ring currents. It is shown that electromagnetic radiation propagates as a wave inside a cone along the magnetic field. The field propagation outside the cone is described by a diffusion law. The spatio-temporal characteristics of the signal are determined by the ionospheric conductivities. 相似文献
2.
S. Ya. Mikhailov 《Radiophysics and Quantum Electronics》2009,52(12):843-853
When the ionosphere is sounded by a chirp signal, the information source is the amplitude and phase modulation of the signal
due to its propagation in the ionospheric radio channel. We propose the method of received-signal demodulation which allows
us to use the chirp ionosonde as a gauge for impulse characteristic and transfer function of the ionospheric radio channel.
Operation of the chirp ionosonde is numerically simulated and estimates of intrinsic accuracy in measuring the mentioned characteristics
are obtained. 相似文献
3.
Ivanov V. A. Kurkin V. I. Nosov V. E. Uryadov V. P. Shumaev V. V. 《Radiophysics and Quantum Electronics》2003,46(11):821-851
We present a review of materials related to a chirp ionosonde and its application in the ionospheric research. The principle of operation of an ionosonde radiating a continuous signal with linear frequency modulation is described. The chirp-ionosonde resolution and gain in the signal-to-noise ratio are estimated. Examples of applying a chirp ionosonde to problems of ionospheric HF-wave propagation are considered. Prospects for ionospheric research on the basis of a network of oblique chirp-sounding paths are discussed. 相似文献
4.
A survey of ionospheric effects on space-based radar 总被引:2,自引:0,他引:2
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6.
N. V. Ilyin M. A. Davydenko V. V. Khakhinov 《Radiophysics and Quantum Electronics》2007,50(5):352-359
We model theoretically the received spectrum in the case of sounding of the ionospheric HF radio channel by a chirp signal.
It is shown that the result of processing of an individual time sample of the received signal is equivalent to the sounding
of the radio channel by a complex narrow-band pulsed signal such that the group delays of its propagation modes determine
the maxima in the received spectrum. We analyze the quadrature components of realizations of the received signal at the intermediate
frequency at the bandpass-filter output in the receiving channel of the chirp ionosonde. The results of our analysis show
the possibility of reconstructing the transfer function of a HF radio channel in the sounding-frequency band for the delay
range determined by the characteristics of the intermediate-frequency bandpass filter. We propose a method for reconstructing
the transfer function of the ionospheric radio channel, which involves supplementing the circuit of primary processing of
the signal by a corrective digital filter with specified amplitude-frequency and phase-frequency characteristics. The proposed
method can be used for all operating regimes of the chirp ionosonde in the case of digital recording and processing of signals.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 5, pp. 387–395, May 2007. 相似文献
7.
8.
The variation in the spectrum of an infrasonic signal emitted by a point source during its propagation from Earth’s surface to ionospheric altitudes and its effect on the ionosphere are considered from model calculations. 相似文献
9.
I. V. Karpov F. S. Bessarab Yu. N. Korenkov V. V. Klimenko M. V. Klimenko 《Russian Journal of Physical Chemistry B, Focus on Physics》2016,10(1):117-126
The results of numerical simulations of the effects of a sudden stratospheric warming (SSW) in January 2009 are examined. The calculations are performed within the framework of the Global Self-Consistent Model of the Thermosphere, Ionosphere, Protonosphere (GSM TIP), which calculates the parameters of the neutral and charged components of the upper atmosphere. An analysis of the numerical simulation results showed that the perturbation of mesospheric tidal and planetary waves significantly affects the structure of variations of the thermosphere at altitudes below 150 km. At higher altitudes, the characteristics of planetary and tidal waves in the thermosphere are practically insensitive to the corresponding mesospheric perturbations. The calculated space–time structure of ionospheric perturbations caused by mesospheric and planetary tidal waves is in qualitative agreement with observation data. The results show that the main reason for the observed ionospheric effects is the perturbation of the electric fields in the dynamo region. However, the calculated magnitudes of the ionospheric effects produced by the SSW are at least two- to threefold weaker than the observed. It is assumed that, in order to achieve a quantitative agreement between simulation and experimental results on the ionospheric effects of the SSW, it is not enough to consider only the dynamics of planetary and tidal waves in the mesosphere. An additional source of the perturbation of the thermosphere and ionosphere during the SSW may be associated with the propagation of internal gravity waves from the lower atmosphere and their dissipation in the thermosphere. 相似文献
10.
The effect of the generation of ULF variations of the magnetic field during the propagation of acoustic-gravitaty waves (AGW)
in the ionosphere is analyzed within a simple model. It is shown that AGW-induced ionospheric irregularities can significantly
contribute to the ground magnetic field variations. Some changes in ULF variations associated with seismic events are considered
as application of this mechanism. 相似文献
11.
E. N. Ermakova D. S. Kotik L. A. Sobchakov S. V. Polyakov A. V. Vasil'yev T. Bosinger 《Radiophysics and Quantum Electronics》2005,48(9):700-710
We present the results of experiments on studying of characteristics of the ULF/ELF signals generated by the Kola ground facility.
Signals were detected at different distances from the source. The amplitude and polarization parameters of the signal are
plotted as functions of the distance and direction to the source, which allows us to determine the efficiency of using this
facility for receiving signals at points with different geographic coordinates and for different levels of background low-frequency
noise. It is found that the signal characteristics are sensitive to variations in the parameters of the ionospheric layers
and comprise information on the inhomogeneous structure of the Earth's crust under the source.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 9, pp. 788–799, September 2005. 相似文献
12.
Bakhmet'eva N. V. Belikovich V. V. Benediktov E. A. 《Radiophysics and Quantum Electronics》2001,44(12):924-934
We present new results of our studies of the irregular structure of the ionosphere using artificial periodic inhomogeneities (APIs) of the ionospheric plasma. The observations were carried out from 9:00 to 17:00 in August 10–12, 1999 with a height step of 0.7 km and digital registration and real-time processing of the signal quadratures. It is shown that in many cases, the amplitude of the scattered signal is determined by the interference of radio waves scattered on APIs and on natural ionospheric formations including sporadic layers and large-scale natural irregularities. This allows one to study the irregular structure of the lower ionosphere by analyzing height-time dependences of the amplitude and phase of the scattered signal. 相似文献
13.
V. L. Frolov L. M. Erukhimov G. P. Komrakov E. N. Sergeev B. Thidé P. A. Bernhardt L. S. Wagner J. A. Goldstein G. Selcher 《Radiophysics and Quantum Electronics》1997,40(5):371-386
We present measured characteristics of the artificial ionospheric radio emission (AIRE), which were obtained experimentally
using additional heating of the ionospheric F-region by O-polarized waves. It is shown that the observed enhancement of intensity
of the broad upshifted maximum (BUM) of the AIRE can result from the influence of electrons accelerated in the plasma: esonance
region on its generation. An empirical model of the phenomenon observed is developed. It is concluded from experimental results
that the BUM has a complex structure and only one of its components produces the above emission enhancement. We show the possibility
of using the AIRE in additional heating of ionospheric plasma for diagnostics of artificial ionospheric turbulence and investigation
of the features of perturbation propagation along the geomagnetic field lines.
Radiophysical Research Institute, Nizhny Novgorod, Russia. Institute of Space Physics, Uppsala, Sweden. The Naval Research
Laboratory, Washington, D.C. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 5, pp. 561–585,
May, 1997. 相似文献
14.
We specify the formulation of the problem of reconstructing the plasma frequency height distribution from a given height-frequency characteristic (HFC) for a spherically symmetric isotropic ionosphere. We propose a numerical algorithm for solving the problem of correctly processing the region of near-critical frequencies of ionospheric layers. On this basis, we study the discernibility of plasma frequency profiles (PFPs) satisfying a given HFC when the properties of an obliquely propagating HF signal are analyzed. 相似文献
15.
We report on the results of observations of reflected SW signals by vertical sounding (VS) of the ionosphere in Zimenki, Nizhny Novgorod region, in the summers of 1994 and 1995. We discovered an anomalous increase in the multipath propagation of the received SW signals during ionospheric F-spread: The duration of a multipath reflected signal increased considerably when we used a highly directional antenna compared to the case of a weakly directional antenna. The fast amplitude fluctuation index increased with increasing delay of the reflected SW signals. The observations are interpreted in terms of a stochastic model of midlatitude F-spread as the phenomenon of multipath radio wave scattering (reflection) from large-scale electron density inhomogeneities under conditions of a strongly developed inhomogeneous structure of the ionosphere.Radiophysical Research Institute, Nizhny Novgorod. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, No. 10, pp. 1064–1070, October, 1995. 相似文献
16.
D. L. Pasmanik A. G. Demekhov V. Yu. Trakhtengerts E. E. Titova M. J. Rycroft 《Radiophysics and Quantum Electronics》2009,52(4):252-261
We study theoretically the propagation of lower-hybrid resonance (LHR) waves in the auroral ionospheric plasma. The ray-tracing
technique is used to study the properties of LHR wave propagation with account of a large-scale inhomogeneity both along and
across the geomagnetic field. It is shown that wave refraction in such an inhomogeneous medium can result in direct transformation
of LHR waves whose wave normals make large angles with the geomagnetic field into whistler-mode waves, whose wave vectors
are close to the geomagnetic-field direction and which can therefore pass through the ionosphere to the ground. The parameters
of LHR waves which can thus be transformed into whistler-mode waves are found. The transformation process considered can be
important for interpreting ground-based observations of ELF waves.
Deceased.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 52, No. 4, pp. 279–289, April 2009. 相似文献
17.
G. G.Vertogradov V. P. Uryadov E. G. Vertogradova A. A. Ponyatov 《Radiophysics and Quantum Electronics》2010,53(3):161-170
We present the results of experimental studies of propagation of short radio waves on a long transequatorial path of Laverton
(Australia) — Rostov-on-Don, which were obtained with the help of an ionosonde/direction finder with chirp modulation of the
signal. It is shown that conditions for propagation of anomalous signals by means of sideband reflection of radio waves from
the Himalayan Hills and the Plateau of Iran and also due to scattering of radio waves from the high-latitude ionosphere of
the northern hemisphere are realized on the given path. The propagation of radio waves is modeled with allowance for their
scattering by anisotropic magnetic field-aligned irregularities of a high-latitude ionosphere, which are located on the northern
wall of the main ionospheric trough of the F layer. It is shown that the results of the experiment agree well with the calculated data. 相似文献
18.
We present the results of studying the multifractal structure of intermittency in a developed ionospheric turbulence during
special experiments on radio-raying of the midlatitude ionosphere by signals from orbital satellites in 2005–2006. It is shown,
in particular, that the determination of multidimensional structural functions of the energy fluctuations of received signals
permits one to obtain the necessary information on multifractal spectra of the studied process of radio-wave scattering in
the ionosphere. Experimental data on multifractal spectra of slow fluctuations in the received-signal energy under conditions
of a developed small-scale turbulence are compared with the existing concept of the radio-wave scattering within the framework
of the statistical theory of radio-wave propagation in the ionosphere. It is inferred that under conditions of a developed
ionospheric turbulence, the multifractal structure of the intermittency of slow fluctuations in the received-signal energy
is a consequence of the intermittency of small-scale fluctuations in the electron number density of the ionospheric plasma
on relatively large spatial scales of about several ten kilometers.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 6, pp. 485–493, June 2008. 相似文献
19.
R. Bhattacharya A. Nag R. Guha A. Bhoumick S. De A. B. Bhattacharya 《Indian Journal of Physics》2010,84(11):1587-1595
The results of investigation of the variation of radio signal strengths during the solar eclipse on July 22, 2009 are reported
in this paper. Observations of the radio signals transmitted from different radio stations at different frequencies and received
at a particular observing site indicate a distinct change in signal strength around the time the eclipse umbra passes the
propagation paths. The three types of variations in the eclipse day and particularly during its peak period are different
from propagation under normal condition. The phenomena of signal variations, the noted “Inverted U-shape“ at one of the frequencies
before the occurrence of the eclipse and 13 to 15 minutes time difference between the enhancement of the signal strength and
the onset of eclipse are some interesting characteristics. The results are interpreted by ionospheric D-layer behavior at
such times. 相似文献
20.
Uryadov V. P. Ponyatov A. A. Rozanov S. V. Poddel'sky N. P. Poddel'sky I. N. Tsukanov A. V. 《Radiophysics and Quantum Electronics》2001,44(3):235-242
We present experimental results on HF-radiowave propagation features for the midlatitude Khabarovsk--Nizhny Novgorod and subauroral Magadan--Nizhny Novgorod paths using chirp ionospheric sounding. The spatial correlation of the maximum observed frequency (MOF) is measured. It is found that at 07:00-14:00 MSK in quiet days with a magnetic-activity index Kp 2 the correlation coefficient amounts to 0.75-0.95. With increase in disturbance for Kp 3, the correlation coefficient decreases to about 0.65-0.8. In the evening and night hours (20:00-02:00 MSK), the MOF spatial correlation decreases considerably, and reverses sign in some cases, which can be an indication of the different mechanisms of HF-signal field formation on the paths considered. Signal characteristics as functions of the path orientation relative to the ionospheric trough are analyzed. It is shown that at 20:00-02:00 MSK, the Magadan-Nizhny Novgorod path passes near the northern wall and the Khabarovsk-Nizhny Novgorod path, near the southern wall of the trough. At that time, the HF-radiation propagation was implemented through standard hop modes on the mid-latitude path and through the high-angle ray (Pedersen mode) on the subauroral path. The signal diffusivity on the Magadan-Nizhny Novgorod path exceeds by about two or three times the signal diffusivity on the Khabarovsk-Nizhny Novgorod path. The experimental data are compared with the results of simulation of the signal diffusivity due to HF-radiowave scattering by the magnetic-field-aligned ionospheric irregularities located in the vicinity of the southern boundary of the auroral oval. 相似文献