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1.
We consider the problem of diagnostics of the local structure of small-scale ionospheric turbulence using the multifractal
analysis of received signals from the Earth’s orbital satellites after the radio sounding of the inhomogeneous ionosphere
by these signals. In particular, it is shown that analysis of the multifractal structure of the received-signal amplitude
records by the method of multidimensional structural functions allows one to determine the indices of the multipower local
spectra of the small-scale ionospheric turbulence, which are inherent in it due to the nonuniform spatial distribution of
small-scale fluctuations of the electron number density. It is noted that information on the multipower spectrum of small-scale
ionospheric turbulence is not available for the conventional radio scintillation method based on the classical spectral analysis
of received signals during the remote radio sounding of the ionosphere. At the same time, the method of multidimensional structural
functions is efficient under conditions of actual nonstationarity of the process of scattering of the HF radio waves by the
randomly inhomogeneous ionospheric plasma. The method of multidimensional structural functions is used for the multifractal
processing of received signals of orbital satellites during special experiments on radio sounding of the midlatitude ionosphere
under natural conditions and its modification by high-power HF radio waves. First data on the indices of the multipower local
spectra of small-scale ionospheric turbulence are obtained.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 52, No. 1, pp. 14–22, January 2009. 相似文献
2.
We present the results of the first studies of the fractal structure of the developed small-scale ionospheric turbulence (SSIT)
during special experiments on radio-raying of the midlatitude ionosphere by signals from orbital satellites in 2005–2006.
It is established that under conditions of developed turbulence, typical values of the fractal dimension of the space occupied
by natural SSIT inhomogeneities are, as a rule, close to the topological dimension of their embedding space, and the true
values of the spectral index of isotropic SSIT only slightly differ from the corresponding generally accepted nominal values
in the embedding space. Nevertheless, even small differences in the mentioned parameters detected in the experiment witness
a sharply nonuniform distribution of the local fractal structures of the developed SSIT in space. We propose a stochastic
model of the nonstationary process for fast amplitude fluctuations of signals during their propagation in the ionosphere with
nonuniform spatial distribution of small-scale electron-density fluctuations. Eventually, namely this nonuniform distribution
of small-scale electron-density fluctuations leads to the specific multifractal structure of the amplitude records of received
signals.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 4, pp. 287–294, April 2008. 相似文献
3.
We consider the problem of obtaining reliable values of the local-spectrum indices of the electron number density fluctuations
for small-scale ionospheric turbulence. It is shown that the use of a multifractal analysis in combination with the synchronous
correlation processing of the received signals in the experiments on remote radio sounding of the ionosphere by satellite
signals permits one to solve the posed problem. In this case, the true values of the local-spectrum indices of small-scale
ionospheric turbulence, which are measured in such specialized experiments under natural conditions and during modification
of the ionosphere by high-power HF radio emission, can differ notably from their standard values obtained within the framework
of the classical method of radio scintillations, in which only correlation processing of the data is used.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 7, pp. 571–574, July 2008. 相似文献
4.
V. A. Alimov L. M. Erukhimov E. N. Myasnikov A. V. Rakhlin 《Radiophysics and Quantum Electronics》1997,40(4):294-300
The problem of defining the spectral form of ionospheric irregularities with dimensions from hundreds to thousands of meters
is considered. A generalized model is proposed for the ionospheric turbulence spectrum, taking into account both the anisotropic
properties of the large-scale fraction of irregularities and the dependence of the anisotropy (elongation) of small-scale
irregularities of the upper ionosphere along the Earth magnetic field direction on the transverse scale of those irregularities.
Relations have been derived to determine the basic parameters of the irregularity spectrum of the uppers ionosphere (anisotropy
indices for large-scale and small-scale fractions) and the depth of a thin ionospheric layer through measurement of the spectral
characteristics of amplitude and phase fluctuations of orbital satellite signals. Using this model of the plasma irregularity
spectrum, we can explain consistently many well-known experimental data on spectral characteristics of the phase and amplitude
fluctuations of orbital satellite signals both in the high-latitude and midlatitude ionosphere.
Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika,
Vol. 40, No. 4, pp. 446–456, April, 1997. 相似文献
5.
V. A. Alimov F. I. Vybornov E. N. Myasnikov A. V. Rakhlin 《Radiophysics and Quantum Electronics》2008,51(11):874-879
We show the results of the first experimental studies of the multifractal structure of the developed artificial ionospheric
turbulence. As a result of the special multifractal analysis of the recorded amplitudes of signals from the orbital satellites,
which were obtained during the experiments on radio tomography of the irregularities excited in the ionosphere by the powerful
mid-latitude heating facility “Sura,” it is found that the characteristic multifractal structure of these records is caused
by the nonuniform spatial distribution of the small-scale fluctuations of the electron number density in the artificial irregularities
of the ionospheric plasma. Comparative analysis is performed for the multifractal spectra of fluctuations of both the amplitudes
and energies of signals received from the orbital satellites upon radio transmission probing of the region of artificial ionospheric
turbulence by these signals at three observation points located near the “Sura” heating facility and spaced apart to a distance
of about 100–150 km.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 11, pp. 970–976, November 2008. 相似文献
6.
We consider various theoretical models for the spectrum of small-scale ionospheric turbulence. The particular role of the
generalized model of the ionospheric-turbulence spectrum, which takes into account that the anisotropy (extension) of small-scale
irregularities of the upper ionosphere along the Earth's magnetic field direction depends on the transverse scale of those
irregularities, is emphasized. The results of the. rst target experiments on radio sensing of the midlatitude ionosphere by
signals from on-orbit satellites at frequencies 150 and 400 MHz under conditions of increased solar activity are presented.
The experiments were performed at the radiophysical facility in the Nizhny Novgorod region in 2003. We studied statistical
characteristics of the amplitude fluctuations of the received signals for different angles ϑ between the line of sight from
a satellite to a ground-based reception point and the Earth's magnetic field direction. It was found in the course of the
experiments that the spectrum slope of amplitude fluctuations of the received radiation is a function of the angle ϑ. The
obtained result agrees with the generalized model of the ionospheric-turbulence spectrum and can be an argument in favor of
the pronounced anisotropic structure of small-scale electron-density irregularities of the midlatitude ionosphere under disturbed
geophysical conditions.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 5, pp. 382–387, May 2005. 相似文献
7.
V. A. Alimov F. I.Vybornov E. N. Myasnikov A. V. Rakhlin V. L. Frolov 《Radiophysics and Quantum Electronics》2009,52(9):609-617
We present the results of the experiment on studying the multifractal structure (with inhomogeneity sizes from tens to hundreds
of meters across the Earth’s magnetic field) of the artificial ionospheric turbulence when the midlatitude ionosphere is affected
by high-power HF radio waves. The experimental studies were performed on the basis of the “Sura” heating facility with the
help of radio sounding of the disturbed region of the ionospheric plasma by signals from the Earth’s orbital satellites. The
influence of the magnetic zenith effect on measured multifractal characteristics of the small-scale artificial turbulence
of the midlatitude ionosphere was examined. In the case of vertical radio sounding of the disturbed ionosphere region, the
measured multipower and generalized multifractal spectra of turbulence coincide well with similar multifractal characteristics
of the ionospheric turbulence under natural conditions. This result is explained by the fact that the scattering of signals
by weak quasi-isotropic small-scale inhomogeneities of the electron number density in a thick layer with a typical size of
several hundred kilometers above the region of reflection of high-power HF radio waves gives the major contribution to the
observed amplitude fluctuations of received signals. In the case of oblique sounding of the disturbance region at small angles
between the line of sight to the satellite and the direction of the Earth’s magnetic field, the nonuniform structure of the
small-scale turbulence with a relatively narrow multipower spectrum and small variations in the generalized multifractal spectrum
of the electron number density was detected. Such a fairly well ordered structure of the turbulence is explained by the influence
of the magnetic zenith effect on the generation of anisotropic small-scale artificial turbulence in a thin layer having a
typical size of several ten kilometers and located below the pump-wave reflection height in the upper ionosphere. 相似文献
8.
We present the results of the studies of fractal properties of the small-scale inhomogeneities of traveling ionospheric disturbances
in special experiments on radio-raying of the midlatitude ionosphere by signals from orbital satellites in 2004–2006. Along
with the conventional correlation processing of the received signals, we performed their multifractal analysis, as well as
fractal processing of signals by the correlation-integral method. Important information on fractal properties of the small-scale
turbulence for the least studied part of the upper-ionosphere inhomogeneity spectrum in the interval of characteristic scales
l ≈ 1–10 km is obtained. In particular, it is noted that the fractal structure of these inhomogeneities can be originated
from the nonlinear “destruction” of several large-scale sinusoidal structures in a quasistable traveling disturbance. It is
also noted that the multifractal spectra of amplitude fluctuations of the received signals obtained in the experiments in
different years, in different time of the day, and in different seasons of the observations are quite similar. This is evidence
that intermittency is a universal property of the plasma turbulence, at least for the midlatitude upper ionosphere.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 1, pp. 22–30, January 2008. 相似文献
9.
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
10.
Using the method of radio sounding of the mid-latitude ionosphere by the satellite signals, we study the multifractal structure
of small-scale ionospheric turbulence during a solar eclipse. The measured multipower and generalized multifractal spectra
of small-scale ionospheric turbulence at the initial and closing stages of the eclipse turn out to be almost identical on
the space radio paths with different orientations. This is indicative of a sufficiently high stability of the nonuniform spatio-temporal
distribution of small-scale fluctuations of the ionospheric electron number density under conditions of geophysical disturbances
due to global physical processes in the ionospheric plasma during a solar eclipse.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 52, No. 4, pp. 302–306, April 2009. 相似文献
11.
L. M. Kagan 《Radiophysics and Quantum Electronics》1996,39(3):217-223
We consider Lorentz-type mechanism for growth of LF small-scale turbulence due to generation of local field-aligned electric fields (FAEF) in the ionospheric F-region modified by powerful radio waves. The FAEF are induced by Lorentz-type forces caused by the large-scale pressure structure of the heated volume. We found that small- scale structuring of the large-scale depleted region (the patch) is a function of altitude and that the cross-field scale of small-scale irregularities is definitely determined by the gradient scale length in plasma density. This mechanism allows us to explain the generation of irregularities with scale lengths of 6 m or longer and observations of aftereffects within 30 seconds or longer after the pump switch-off if they are defined by the lifetime of the induced local sources. The predictions of the Lorentz-type mechanism are shown to be consistent with the measurements of the significant growth of DSEE typical times, related to relaxation of heater-induced small-scale irregularities, under conditions of strong natural turbulence observed as F-spread in the ionograms.Published from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 3, pp. 318–328, March, 1996. 相似文献
12.
We report on the results of the first special experiment on radio sounding of the midlatitude ionosphere by signals from in-orbit
satellites at a frequency of 150 MHz under quiet geophysical conditions. Along with the conventional correlation processing,
fractal processing of the received signals was also performed. Using the fractal approach, we obtained first data on the sources
and generation mechanisms of small-scale plasma inhomogeneities of the traveling ionospheric disturbances (TIDs) in the upper
ionosphere. It is noted that the phenomenon of nonlinear “ breaking” of the acoustic-gravity waves entering the ionosphere
from the underlying atmosphere plays the crucial role in the formation of plasma inhomogeneities of the TIDs.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 7, pp. 561–569, July 2006. 相似文献
13.
V. P. Uryadov V. I. Kurkin G. G. Vertogradov V. G. Vertogradov A. A. Ponyatov S. N. Ponomarchuk 《Radiophysics and Quantum Electronics》2004,47(12):933-946
We present the results of experimental studies of the features of HF-signal propagation on oblique-sounding paths in the Eurasian longitude sector between England and Magadan during geomagnetic disturbances. The joint analysis of the satellite data and the data of vertical and oblique sounding of the ionosphere shows that the appearance of additional signals during magnetic disturbances can be stipulated by refraction of radio waves in the region of the auroral oval and the main ionospheric trough as well as by scattering from small-scale magnetic-field-aligned irregularities near the equatorial boundary of the auroral oval. Based on calculations and comparison with experimental data of oblique sounding of the mid-latitude ionosphere, we identify the lateral spreading signals registered on the Magadan — Irkutsk and Inskip (England) — Rostov-on-Don paths as signals scattered by small-scale field-aligned irregularities whose location coincides with the southern boundary of the auroral oval. We show that the Russian and global chirp-ionosonde networks are promising for studying the dynamics of the main ionospheric trough and the auroral oval during geomagnetic disturbances as a manifestation of space weather in the near-Earth environment.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 47, No. 12, pp. 1041–1056, December, 2004. 相似文献
14.
We present the results of studies of the multifractal structure of slow (of duration τ ≈ 10 s) fluctuations of the received-signal
amplitudes in special experiments on radio-raying of the midlatitude ionosphere by signals from orbital satellites in 2004–2006.
It is shown, in particular, that the method of multifractal analysis of amplitude records of the received signals yields information
on the spectrum of large-scale ionospheric inhomogeneities, which is inaccessible for the classical method of radio scintillations.
From the results of measurements with the use of multifractal processing of experimental data, we found that large-scale (tens
of kilometers) quasiregular electron-density inhomogeneities of traveling ionospheric disturbances (TIDs) have a power-law
spectrum. It is exactly the power-law form of the spatial spectrum of large-scale inhomogeneities of TIDs that can be the
reason for the observed multifractal structure of the intermittency of slow fluctuations of the received-signal amplitudes.
However, under conditions of a developed small-scale turbulence of TIDs, the observed multifractal structure of the received
signals is, as a rule, stipulated by the spatial inhomogeneity of the variance of the integral electron-density fluctuations
of small-scale inhomogeneities on scales comparable with the sizes of large-scale inhomogeneities of TIDs.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 3, pp. 191–198, March 2008. 相似文献
15.
V. P. Uryadov G. G. Vertogradov V. G. Vertogradov A. A. Ponyatov V. L. Frolov 《Radiophysics and Quantum Electronics》2004,47(9):646-661
We present the results of radar observations of artificial ionospheric turbulence (AIT) created due to modification of the ionosphere by high-power radio emission from the Sura heating facility (Nizhny Novgorod region, Russia). Measurements were carried out in August 18–22, 2003 in the evening time (16:00–20:00 UT) with the use of over-the-horizon chirp HF radars on the Khabarovsk-Rostov-on-Don, Irkutsk-Rostov-on-Don, Inskip (England)-Rostov-on-Don paths, and also on the Moscow-Rostov-on-Don path for which reference signals of the standard-time RVM station were received. It is found that conditions for propagation of HF signals through the upper ionosphere at frequencies exceeding the maximum usable frequency for standard hop propagation through the F region were realized on the Irkutsk-Sura path in the presence of the powerful sporadic Es layer. The presence of such signals was revealed at the Rostov-on-Don station by receiving radio waves which escape from the altitudes of the ionospheric F region due to scattering by artificial small-scale magnetic-field-aligned irregularities. We studied the ionospheric effects of a magnetic storm occurring during the experiment by using the measurement data of the Doppler frequency shift of signals scattered by artificial ionospheric turbulence. It is shown that during a magnetic storm, the electric field and the drift velocity of irregularities at the altitudes of the F layer over the Sura facility reach values of 8.6 mV/m and 186 m/s, respectively, which are typical of the high-latitude ionosphere. We consider the relation between quasi-periodic oscillations of the Doppler frequency shift of the scattered signal and propagation of magnetohydrodynamic waves excited during the magnetospheric storm.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 47, No. 9, pp. 722–738, September, 2004. 相似文献
16.
V. L. Frolov G. G. Vertogradov V. G. Vertogradov 《Radiophysics and Quantum Electronics》2008,51(4):247-258
We analyze variations in characteristics of the diagnostic stimulated electromagnetic emission of the ionosphere in the evening
hours including the times of sunset both on the Earth’s surface at the observation point and in the ionosphere over it. It
is found that an increase in typical times of evolution of the diagnostic emission begins to be recorded just before the sunset
on the Earth’s surface when the ionosphere is illuminated and its parameters are not significantly changed yet. We state that
the typical times of evolution of the diagnostic emission increase when the pump-wave frequency approaches the critical frequency
of the ionospheric F2 layer, but such an effect is not as significant as when passing from the illuminated to the unilluminated ionosphere. It
is established that at the stage of diagnostic sounding the pump-wave pulse power does not exert any notable influence on
the first (fast) stage of relaxation of small-scale artificial ionospheric irregularities, but can increase the decay time
of the irregularities at the second (slow) stage of relaxation. Capabilities of the method for a study of artificial plasma
turbulence using the diagnostic stimulated electromagnetic emission are discussed.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 4, pp. 273–286, April 2008. 相似文献
17.
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
18.
Some distinctive features in the behavior of small-scale artificial ionospheric irregularities at mid-and high latitudes 总被引:1,自引:0,他引:1
N. F. Blagoveshchenskaya T. D. Borisova V. A. Kornienko V. L. Frolov M. T. Rietveld A. Brekke 《Radiophysics and Quantum Electronics》2007,50(8):619-632
We present the results of experimental studies of some features in the behavior of small-scale artificial irregularities (SSAIs)
at mid-and high latitudes based on the “Sura” and EISCAT/HEATING HF facilities. Observations were performed by the method
of aspect scattering using a network of diagnostic paths having a common reception point located near St. Petersburg. We found
that an extremely long duration of the second (slow) stage of SSAI relaxation of up to 5 min occurs in the evening hours when
the ionosphere above the “Sura” facility is illuminated by the Sun, but the solar terminator travels through the magnetically
conjugated ionosphere. The conjecture is made that the processes initiated by the terminator are mostly responsible for secondary
ionospheric turbulence maintaining the irregularities above “Sura.” A drastic increase in the Doppler spectra width of the
scattered signals is revealed when the magnetically conjugate point of the ionosphere is located on the shade side of the
terminator, but the ionosphere above the “Sura” facility is still lighted. It is assumed that the “ run away” of photoelectrons
from the day to the night side could reduce the threshold of excitation of artificial irregularities, leading to an increase
in their intensity. The presence of fairly intense scattered signals was detected from the “Sura” and EISCAT/HEATING experimental
results both under conditions of pulsed HF heating after continuous heater-on periods and cycled HF heating by short pulses.
In the case of pulsed heating by short pulses with duration τp < 100 ms and average radiated power Pa below the threshold power Pthr of the SSAI generation cutoff the irregularities can be maintained due only to striction parametric instabilities. The excitation
of irregularites under the cycled HF pumping with the pulse duration τp = 384 ms for Pa comparable with Pthr was detected. The aspect-angle dependence, or the so-called magnetic zenith effect, was found in the SSAI intensity. The
residual turbulence aftereffects played a significant role in the SSAI development.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 8, pp. 678–694, August 2007. 相似文献
19.
V. L. Frolov G. P. Komrakov V. E. Kunitsyn A. M. Padokhin A. E. Vasiliev G. A. Kurbatov 《Radiophysics and Quantum Electronics》2010,53(7):379-400
We present the results of experimental studies of the properties of the plasma-density disturbances created during heating
of the ionospheric F2 region by high-power HF radio waves radiated by the “Sura” heating facility (Radiophysical Research Institute, Nizhny Novgorod).
These experiments are specific in that they were performed in a sunlit (daytime) ionosphere when the generation of ionospheric
turbulence has specific features and the turbulence intensity level is low enough. The plasma-density disturbances induced
by high-power HF radio emission were sounded by signals of the GPS satellites, the line of sight to which crossed different
parts of the disturbed ionosphere region. Threshold powers of the excitation of artificial plasma-density variations as well
as spatial, temporal, spectral, and energy characteristics of the generated disturbances are determined. 相似文献
20.
E. D. Tereshchenko A. N. Milichenko V. L. Frolov R. Yu. Yurik 《Radiophysics and Quantum Electronics》2008,51(11):842-846
We present the results of first studies of the modification of the ionosphere by high-power HF radiation, which were obtained
using signals of high-orbit GPS/GLONASS navigation satellites. Enhancement of the ionospheric modification in the magnetic-field
direction was observed for the first time. This leads to a total decrease in electron number density and the formation of
electron density irregularities near the magnetic-zenith direction. The efficiency of using GSP/GLONASS satellite signals
for the studies of the ionosphere modified by HF radiation is demonstrated. Prospects for further studies in this field are
discussed.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 11, pp. 934–938, November 2008. 相似文献