共查询到20条相似文献,搜索用时 46 毫秒
1.
E. D. Tereshchenko R. Yu. Yurik T. K. Yeoman T. R. Robinson 《Radiophysics and Quantum Electronics》2008,51(11):858-861
We present the first results of observations of the stimulated electromagnetic emission (SEE) in the ionosphere modified by
the Space Plasma Exploration by Active Radar (SPEAR) heating facility. Observation of the SEE is the key method of ground-based
diagnostics of the ionospheric plasma disturbances due to high-power HF radiation. The presented results were obtained during
the heating campaign performed at the SPEAR facility in February–March 2007. Prominent SEE special features were observed
in periods in which the critical frequency of the F
2 layer was higher than the pump-wave frequency (4.45 MHz). As an example, such special features as the downshifted maximum
and the broad continuum in the region of negative detunings from the pump-wave frequency are presented. Observations clearly
demonstrate that the ionosphere was efficiently excited by the SPEAR heating facility despite the comparatively low pump-wave
power.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 11, pp. 951–955, November 2008. 相似文献
2.
We employ artificial neural networks (ANNs) to develop an algorithm yielding 1-, 2-, 3-, 12-, and 24-hour forecasts of the critical frequency of the ionospheric F2 layer. A search for suitable training set and ANN architecture is performed. The use of auxiliary input data, such as the solar-wind and interplanetary magnetic-field parameters, as well as the geomagnetic-activity indices, makes it possible not only to improve the prediction efficiency but also to find some regularities in the critical-frequency behavior. The results of this work can be applied to the prompt correction of the ionosphere model, aimed at improving the ionospheric HF radio communication.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 1, pp. 1–15, January 2005. 相似文献
3.
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
4.
N. F. Blagoveshchenskaya T. D. Borisova V. A. Kornienko A. S. Janzhura A. S. Kalishin T. R. Robinson T. K. Yeoman D. M. Wright L. J. Baddeley 《Radiophysics and Quantum Electronics》2008,51(11):847-857
We present the results of experimental studies of specific features in the behavior of small-scale artificial field-aligned
irregularities (AFAIs) and the DM component in the spectra of stimulated electromagnetic emission (SEE). Analysis of experimental
data shows that AFAIs in the polar ionosphere are generated under different background geophysical conditions (season, local
time, the presence of sporadic layers in the E region, etc.). It is shown that AFAIs can be excited not only in the F region, but also in “thick” sporadic E
s layers of the polar ionosphere. The AFAIs were observed in some cycles of heating when the HF heater frequency exceeded the
critical frequency by 0.3–0.5 MHz. Propagation paths of diagnostic HF radio waves scattered by AFAIs were modelled for geophysical
conditions prevailing during the SPEAR heating experiments. Two components, namely, a narrow-banded one with a Doppler-spectrum
width of up to 2 Hz and a broadband one observed in a band of up to 20 Hz, were found in the sporadic E
s layer during the AFAI excitation. Analysis of the SEE spectra shows that the behavior of the DM component in time is irregular,
which is possibly due to strong variations in the critical frequency of the F
2 layer from 3.5 to 4.6 MHz. An interesting feature observed in the SPEAR heating experiments is that the generation of the
DM component was similar to the excitation of AFAIs when the heater frequency was up to 0.5 MHz higher than the critical frequency.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 11, pp. 939–950, November 2008. 相似文献
5.
We report on the results of studying the lower ionosphere by a method based on the resonant scattering of radio waves by artificial
periodic inhomogeneities of the ionospheric plasma. Different aspects of studying the sporadic E layer such as the influence of the vertical transfer on its formation, the possibility of examination of its ion composition,
and the influence of the ionosphere heating on the layer characteristics are discussed. The results of determining the parameters
of the E
s layer and some characteristics of the lower ionosphere during the creation of artificial periodic inhomogeneities at two
frequencies are presented.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 11, pp. 956–969, November 2008. 相似文献
6.
V. L. Frolov V. O. Papoport G. P. Komrakov A. S. Belov G. A. Markov M. Parrot J. L. Rauch E. V. Mishin 《Radiophysics and Quantum Electronics》2008,51(11):825-833
We report on the French DEMETER and American DMSP satellite measurements of largescale field-aligned plasma-density perturbations
(ducts) induced in the topside ionosphere by the ionospheric F
2-layer pumping by means of high-power HF radio waves from the “Sura” heating facility. Characteristics of such plasma perturbations
and conditions of their formation are determined.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 11, pp. 915–924, November 2008. 相似文献
7.
N. V. Bakhmet'eva V. V. Belikovich L. M. Kagan A. A. Ponyatov A. V. Tolmacheva M. C. Kelley M. J. Nicolls 《Radiophysics and Quantum Electronics》2005,48(9):673-685
We present the results of studying the lower ionosphere in 2000–2004 at the “Sura” heating facility by the method of resonance
scattering of radio waves from artificial periodic inhomogeneities of the ionospheric plasma. Experimental data on a study
of the sunset–sunrise phenomena in the ionospheric D region and the possibility of determining the concentrations of atomic
oxygen and excited molecular oxygen are discussed. The results of studying the sporadic layers of ionization are presented
and the method for a study of ion composition of the Es layer is discussed. Data of the August 2004 experiments on a study of the influence of heating the ionosphere on the Es layer and characteristics of artificial periodic inhomogeneities are presented. Prospects for further research are discussed.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 9, pp. 757–771, September 2005. 相似文献
8.
Summary A study is made of theF2-layer effect of magnetospheric substorms over the Mediterranean area using data from several ionospheric stations for selected
events in the current sunspot cycle 21. The night-time enhancements in the critical frequency of theF2-layer (f
0
F2) and the total electron content (TEC) have been found with both premidnight and postmidnightf
0
F2 peaks and a subsequent decrease in the minimum virtual height of theF region (h′F). It is found that the enhancements occur through the nights under steady geomagnetic conditions and that the time at which
it is seen at Rome and Grocka ionospheric stations is progressively earlier as geomagnetic activity increases. It has been
further shown that this type of thef
0
F2 night-time increases is not always accompanied by an increase in TEC, although the reverse holds true during the nights
of increased substorm activity. The fact that the considerable variability inf
0
F2, TEC andh′F at the onset of the substorm expansion are preceded by the ionospheric dynamics associated with these observations can be
very useful in the identification of precursor indicative of short-term variations of ionospheric propagation conditions. 相似文献
9.
A theoretical analysis of the vertical propagation of large-scale wave disturbances in the F region and outer ionosphere is
presented. The analysis has included all the major factors influencing the dynamics of the ionospheric plasma under mid-latitude
conditions. It is shown that the disturbances propagating downward in a strongly inhomogeneous medium rise in intensity up
to the heights of the F2-layer maximum and are damped then in the lower layers of the ionosphere. This mechanism can be considered a source responsible
for the inhomogeneous structure of the upper ionosphere.
State University, Irkutsk, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 9, pp.
1086–1092, September, 1998. 相似文献
10.
We consider the features of propagation of decametric radio waves along the transpolar ionospheric paths. The results of recording
round-the-world trip echo signals, which was performed during the many-hour sessions in November and December 1971, are analyzed.
A facility emitting waves at the maximum usable frequency in the zero-azimuth direction and recording the signal arriving
from the opposite direction, which was located in the south of Ukraine, was used. The data obtained on November 23, 1971 for
the radiation frequencies f
o = 16–17 MHz are considered a standard example. We also present the results of calculating the diurnal variation in the maximum
usable frequency of the F
2 layer for a radio-path hop of 4000 km in length in the forward and backward paths Novorossiysk–USA north-west coast in May
1980, which were obtained by the standard methods and correspond to the experimental data. It is shown that the obtained data
can be interpreted on the basis of radiophysical phenomena, namely, (i) the formation of a grazing radio wave near the top
of the first hop with a length of 3000–4000 km for the radiation at the maximum usable frequency and (ii) the night-time retaining
of the daytime properties of the F
2 region in the case of oblique heating by a high-power radio wave. The performed study allowed us to estimate the possibility
of the Alaska HAARP facility to emit to the territory of the Russian Federation.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 52, No. 2, pp. 118–127, February 2009. 相似文献
11.
The times of reversal of east-west electrostatic field in the ionosphere near the equator in the Indian zone have been estimated
from the measurements of ionospheric drift at Thumba. The reversal of electric field in the morning from westward to eastward
is delayed with respect to the sunrise at 100 km by 1.5 hr during winter and by about 3 hr during summer months. The reversal
in the evening from eastward to westward occurs around 2100 hrs,i.e., well after sunset during winter months and around 16–17 hrs,i.e., well before sunset during summer months. The electric field in the American zone is known to reverse 1–2 hr after the sunrise
and sunset at 100 km; the duration of daytime eastward electric field varies with season between 12 and 16 hr. In the Indian
zone, duration of the eastward field during the J months is only 8 hr. These longitudinal differences in the reversal times
of electrostatic field are suggested to be the cause of longitudinal differences in the equatorial ionosphere,viz., high incidence of blanketing sporadicE layer in the Indian zone and the longitudinal differences in the occurrence of spreadF. 相似文献
12.
S. S. Matyugov O. I. Yakovlev V. A. Anufriev 《Radiophysics and Quantum Electronics》2008,51(3):161-169
We analyze characteristics of sporadic layers in the equatorial ionosphere using the results of radio occultation sounding
on the paths between GPS satellites and the CHAMP low-orbiting satellite during the solar flare in October–November 2003.
Variations in the amplitude and phase of signals during the lower-ionosphere sounding are studied. It is shown that the use
of amplitude and phase data allows one to obtain parameters of the sporadic ionospheric structures. The data on the occurrence
frequency, height, thickness, and intensity of the Es layers in the daytime and nighttime equatorial ionosphere are presented.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 3, pp. 181–190, March 2008. 相似文献
13.
V. L. Frolov D. I. Nedzvetsky V. P. Uryadov V. A. Ivanov D. V. Ivanov A. R. Lashchevsky N. V. Ryabova 《Radiophysics and Quantum Electronics》2008,51(5):331-338
We present the results of studying the properties of artificial F-spread that appears on ionograms during heating of the ionospheric
F2 region by a high-power O-mode radio wave. It is shown that the regions of resonant interaction of a high-power radio wave
with plasma, where the pump-wave energy is almost totally absorbed and the plasma is subject to intense heating, affect significantly
the development of a self-focusing instability of a high-power radio wave and the generation of middle-scale (with characteristic
scales across the magnetic field l⊥ ≈ 0.4–1.5 km) artifical ionospheric inhomogeneities. It is established that the intensity of such inhomogeneities depends
on the sign and magnitude of detuning of the pump-wave frequency with respect to the electron gyroresonance harmonic frequency
Δf = fPW − nfce and has the minimum value for Δf ≈ −20 kHz, thus demonstrating the asymmetry of the gyroharmonic properties of their excitation
mechanism. Relationship between the observed phenomena and known characteristics of the artificial ionospheric turbulence
for fPW ≈ nfce is analyzed.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 5, pp. 367–375, May 2008. 相似文献
14.
N. A. Barkhatov O. M. Barkhatova G. I. Grigor’ev 《Radiophysics and Quantum Electronics》2012,55(6):382-390
We obtain dispersion relations for magnetogravity waves in the ionosphere with allowance for the combined influence of magnetic field, gravity, and finite conductivity within the framework of the hydrodynamic approximation. The required conditions are fulfilled in the ionosphere at altitudes over or about 250 km. The auroral electrojet is considered as a source of magnetogravity waves which are frequently observed as traveling ionospheric disturbances. The contribution of magnetogravity waves to the ionospheric disturbances is determined on the basis of analyzing the data from the vertical sounding of the ionospheric F2 layer and the geomagnetic disturbances along the chosen magnetic meridian and on its sides. The features of the obtained dynamic spectra of magnetogravity waves agree with the characteristic frequencies and velocities determined by the calculated dispersion curves. As a result, we confirm the fact that magnetogravity waves stipulate some traveling ionospheric disturbances and can be used for diagnostics of the ionospheric parameters. 相似文献
15.
G. N. Boiko S. M. Grach E. N. Sergeev G. P. Komrakov N. A. Mityakov K. Groves 《Radiophysics and Quantum Electronics》1999,42(7):601-608
On October 24, 1997, from 16:00 to 19:30 LT, during experiments on the artificial mofification of ionosphere by powerful HF
radiation using spaced heating, we recorded twice a significant (tens of percent) decrease of the electron number density
in the F-layer, synchronous with the operation of the heating trnasmitters. The critical frequency of this layer decreased
by 10–20%. This points to the possibility of artificial generation of large-scale inhomogeneities of the ionospheric plasma
density using spatially split heating.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 7, pp. 682–690, January 1999. 相似文献
16.
A. A. Ponyatov V. P. Uryadov V. A. Ivanov D. V. Ivanov A. G. Chernov V. V. Shumaev Yu. N. Cherkashin 《Radiophysics and Quantum Electronics》1999,42(4):269-277
We present the results of experimental studies of the influence of artificial ionospheric disturbances on HF signals used
for oblique sounding of the disturbed volume. The measurements have been performed by a chirp ionosonde over the path Yoshkar-Ola-“Sura”-niznhy
Novgorod with length 234 km. We found the 2F2 mode to disappear (attenuation up to 20 dB) when the ionosphere is influenced
by a vertical powerful radiation in the ordinary mode with long (15 min each) heating and pause intervals. Modeling of the
observed effect was carried out. The calculations agree well with experimental data if the traveling ionospheric disturbances
(TID) with vertical and horizontal scales lz∼20 km and lx∼50 km, respectively, and the relative disturbance of the electron density δN∼0.2–0.3 are amplified (generated) during the
ionosphere heating.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 4, pp. 303–313, April 1999. 相似文献
17.
We present the results of new studies of the sporadic E layer in the case of heating of the ionosphere by high-power HF radio
emission. The measurements were performed at the “Sura” heating facility. Ionosphere was modified by high-power radio emission
from the “Sura” facility and was sounded by the probing radio waves of the same frequency and mode. The heating of the ionosphere
resulted in the formation of artificial periodic inhomogeneities, and an increase in the intensity of all signals scattered
by the D, E, and F regions and the sporadic E layer by 5–20 dB was observed. The increase was observed during heating of the
ionosphere by each magnetoionic component, but was smaller for heating by an ordinary-mode wave. This effect was resonant
and disappeared as a result of the frequency detuning down to 85 kHz. During the ionospheric modification, the signal-intensity
increased due to modulation of the natural profile of the electron number density by the artificial periodic structure.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 8, pp. 695–708, August 2007. 相似文献
18.
O. M. Barkhatova 《Radiophysics and Quantum Electronics》2011,54(3):145-158
We study the correlation between variations in the solar–geophysical parameters and variations in the maximum observable frequencies
(MOF) on several ionospheric short-wave oblique-sounding paths. The basic interplanetary space parameters, whose variations
have the greatest impact on the MOF variations on specified paths, are determined. Variations in the Bx and Bz components of the interplanetary magnetic field (IMF) affect the MOFs on the Norilsk—Rostov-on-Don subauroral path. At mid-latitudes,
the influence of the IMF components Bx, By, and Bz is significant on the Inskip—Rostov-on-Don and Irkutsk—Rostov-on-Don paths. On the Cyprus—Rostov-on-Don low-latitude path,
the modulus of the IMF has the most pronounced effect. The density and velocity of solar wind manifest themselves in MOF variations
on all paths. The technique of MOF retrieval by a neural network on the Cyprus—Rostov-on-Don and Irkutsk—Rostov-on-Don paths
using the MOF data of the Inskip—Rostov-on-Don path is developed with allowance for the influence of the interplanetary space
parameters. The retrieval efficiency of this technique is no less than 80%. 相似文献
19.
20.
V. L. Frolov V. V. Chugurin G. P. Komrakov N. A. Mityakov E. N. Myasnikov V. O. Rapoport E. N. Sergeev V. P. Uryadov F. I. Vybornov V. A. Ivanov V. V. Shumaev A. M. Nasyrov I. A. Nasyrov K. M. Groves 《Radiophysics and Quantum Electronics》2000,43(6):446-468
Experimental studies of the features of artificial ionospheric turbulence was performed at the “Sura” heating facility in
August 1998 using numerous diagnostic tools, such as scintillation, chirp-sounding, backscattering, and stimulated electromagnetic
emission (SEE) measurements, as well as sounding a HF-disturbed volume (DV) by probing waves. It has been found that generation
of strong artificial large-scale irregularities (ALSIs), which manifest themselves through the F-spread on ionograms, scintillations
of the satellite signal propagated through the DV, and amplitude fluctuations of the probing wave sounding the DV, is observed
not only for an overdense heating, at fo≤foF2, but also at higher frequencies fo>foF2≥f
uh
(here fo is the pump-wave frequency, foF2 is the critical frequency of the F2-layer for O-mode electromagnetic wave, and f
uh
is the plasma frequency at the upper-hybrid resonance height). This means that transfer of the pump-wave energy in the plasma
due to the development of thermal parametric (resonance) instability, rather than thermal self-focussing instability, plays
the key role in the ALSI generation in the case where the O-mode HF wave is used for the overdense heating. This conclusion
is also confirmed by the fact that the ALSI generation is suppressed in the gyroharmonic frequency range, which is similar
to the well-studied quenching of the downshifted maximum (DM) in SEE spectra. In this paper, we discuss new ALSI features
revealed by the measurements, as well as the limits by which one can control the ALSI spectrum using complex pumping schemes.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 43, No. 6, pp. 497–519, June, 2000. 相似文献