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1.
E. Ya. Zlotnik A. Klassen H. Aurass K. -L. Klein G. Mann 《Radiophysics and Quantum Electronics》1998,41(1):39-52
Spectrographic and partly imaging observations of three Type II solar radio bursts displaying three drifting bands with frequencies related as 1¬2¬3 are discussed. The radio data of two of these events were simultaneousely recorded by the digital radiospectrograph of the Observatory of Solar Radioastronomy in Potsdam-Tremsdorf and the radioheliograph of the Paris-Meudon Observatory in Nançay. The data allow the brightness temperatures of radio emission in the three frequency bands to be determined. The second harmonic is traditionally explained as a result of coalescence of two plasma waves into an electromagnetic wave at twice the plasma frequency. Two nonlinear merging processes—the coalescence of three plasma waves, and of a plasma wave and an electromagnetic wave at twice the plasma frequency—are considered to explain the occurrence of the third harmonic on Type II dynamic spectra. The analysis shows that both processes can fit the observed brightness temperatures of the second and third harmonic. The first process acts preferably at low phase velocities of plasma waves and sharp electron density gradients in the source, and the second process dominates in the case of high plasma wave phase velocities. It is shown that the occurrence of the third harmonic in type II bursts due to nonlinear processes in the coronal plasma indicates not only a powerful event but also some specific conditions in the shock or foreshock region. Finally, we propose a method to distinguish between the two invoked nonlinear processes by a statistical investigation of Type II burst data. 相似文献
2.
V. V. Zaitsev E. Y. Zlotnik G. Mann H. Aurass A. Klassen 《Radiophysics and Quantum Electronics》1998,41(2):107-114
Herringbone bursts (HB-bursts) are the type III-like fine structure in type II bursts of solar radio emission and are usually
interpreted as plasma radiation arising from fast electrons accelerated by shock waves in the solar corona. In general outline,
the radiation mechanism of HB-bursts is similar to that of type III bursts. However, HB-bursts have brightness temperatures
that are about an order of magnitude higher than those of type III bursts. The frequency drift of BH-bursts is about two or
three times lower than that for type III bursts. All this shows that the fast-electron beams responsible for HB-bursts and
type III bursts differ markedly in their parameters. We calculated expected brightness temperatures of HB-bursts at the fundamental
and second harmonic and compared our results with Culgoora radiometer and radioheliograph data and Tremsdorf spectrograph
data in order to estimate parameters of fast-electron beams generating HB-bursts. We found that the observed brightness temperatures
of HB-bursts give velocities of fast electrons accelerated by shock waves within the limits (0.02–0.17)c. These velocities
are several times lower than those for type III bursts (0.15–0.5)c. The density of the fast electrons responsible for HB-bursts
is in the interval 3·10−6 <nb/n<6·10−5, which exceeds by 1–2 orders of magnitude the relative densities in type III sources. This gives a clue to understanding
the markedly higher brightness temperatures of HB-bursts compared to those of type III bursts. We concluded that the parameters
obtained for the agent exciting HB-bursts favor of turbulence mechanisms of electron acceleration by shock waves in the solar
corona.
Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia; Astrophysical Institute, Potsdam, Germany.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 2, pp. 164–176, February, 1998. 相似文献
3.
S. O. Elyutin A. I. Maimistov I. R. Gabitov 《Journal of Experimental and Theoretical Physics》2010,111(1):157-169
The propagation of the pump and its third harmonic pulses in a cubically nonlinear medium is considered theoretically, provided
that the linear properties of the medium are characterized by a negative refractive index at the pump frequency and a positive
refractive index at the harmonic frequency. For low-intensity interacting waves, the pump and third harmonic pulses propagate
in opposite directions, but sufficiently intense pulses can produce a simulton—a solitary two-frequency wave that propagates
in a certain direction as a single whole. The system of equations is investigated numerically for a model that, apart from
the harmonic generation, includes the second-order group velocity dispersion and the nonlinear self- and cross-phase modulations
of the interacting waves. The separation of the pump and harmonic pulses due to the difference in the directions of their
group velocities and peculiarities of the Manley-Rowe relation for parametric processes in metamedia are discussed. 相似文献
4.
The first numerical simulations are presented for type-III solar radio bursts in the inhomogeneous solar corona and interplanetary space, that include microscale quasilinear and nonlinear processes, intermediate-scale driven ambient density fluctuations, and large scale evolution of electron beams, Langmuir and ion sound waves, and fundamental and harmonic electromagnetic emission. Bidirectional coronal emission is asymmetric between the upward and downward directions, and harmonic emission dominates fundamental emission. In interplanetary space, fundamental and/or harmonic emission can be important. Langmuir and ion sound waves are bursty and the statistics of Langmuir wave energy agree well with the predictions of stochastic growth theory. 相似文献
5.
Solar type II radio bursts are interpreted as the radio signature of shock waves travelling through the solar corona. Some
of these shock waves are able to enter into the interplanetary medium and are observed as interplanetary type II bursts. The
nonthermal radio emission of these bursts indicates that electrons are accelerated up to superthermal and/or relativistic
velocities at the corresponding shocks. Plasma wave measurements at interplanetary shock waves support the assumption that
the fundamental type II radio emission is generated by wave-wave interactions of electron plasma waves and ion acoustic waves
and that the source region is located near the transition region of the shock. Therefore, the instantaneous bandwidth of type
II bursts should reflect the density jump across the shock. Comparing the theoretically predicted density jump of coronal
shock waves (Rankine-Hugoniot relations) and the measured instantaneous bandwidth of solar type II radio bursts it is appropriate
to assume that these bursts are generated by weak supercritical quasi-parallel shock waves. Two different mechanisms for the
accelaration of electrons at this kind of shock waves are investigated in the form of test particle calculations in given
magnetic and electric fields. These fields have been extracted from in-situ measurements at the quasi-parallel region at Earth’s
bow shock, which showed large amplitude magnetic field fluctuations (so-called SLAMS: Short Large Amplitude Magnetic Field
Structures) as constituent parts. The first mechanism treats these structures as strong magnetic mirrors, at which charged
particles are reflected and accelerated. Thus, thermal electrons gain energy due to multiple reflections between two approaching
SLAMS. The second mechanism shows that it is possible to accelerate electrons inside a single SLAMS due to a noncoplanar component
of the magnetic field in these structures. Both mechanism are described in the form of test particle calculations, which are
supplemented by calculations according to adiabatic theory. The results are discussed for circumstances in the solar corona
and in interplanetary space.
Astrophysikalisches Institut, Observatorium für solare Radioastronomie, Potsdam, Germany. Published from Izvestiya Vysshikh
Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 1, pp. 84–104, January, 1998. 相似文献
6.
The processes of acoustical generation of the third-order wave harmonic by nonlinear collinear interaction of the pure third
order and the twofold interaction of the second order are considered. It is shown that, in tomography schemes that are based
on collinear interaction of waves, the interfering signal considerably exceeds the useful signal that brings information on
the acoustical nonlinear parameter of the third order already over short wave propagations. The solutions to the Burgers’
equation and the Riemann waves equation have been numerically modeled to verify theoretical results. It is concluded that,
using the nonlinear third-order effects in diagnostics becomes possible only when the tomography schemes are based on the
noncollinear interaction of waves. 相似文献
7.
Solar type II radio bursts are interpreted as the radio signature of shock waves travelling through the solar corona. Some of these shock waves are able to enter into the interplanetary medium and are observed as interplanetary type II bursts. The nonthermal radio emission of these bursts indicates that electrons are accelerated up to superthermal and/or relativistic velocities at the corresponding shocks. Plasma wave measurements at interplanetary shock waves support the assumption that the fundamental type II radio emission is generated by wave-wave interactions of electron plasma waves and ion acoustic waves and that the source region is located near the transition region of the shock. Therefore, the instantaneous bandwidth of type II bursts should reflect the density jump across the shock. Comparing the theoretically predicted density jump of coronal shock waves (Rankine-Hugoniot relations) and the measured instantaneous bandwidth of solar type II radio bursts it is appropriate to assume that these bursts are generated by weak supercritical quasi-parallel shock waves. Two different mechanisms for the accelaration of electrons at this kind of shock waves are investigated in the form of test particle calculations in given magnetic and electric fields. These fields have been extracted from in-situ measurements at the quasi-parallel region at Earth’s bow shock, which showed large amplitude magnetic field fluctuations (so-called SLAMS: Short Large Amplitude Magnetic Field Structures) as constituent parts. The first mechanism treats these structures as strong magnetic mirrors, at which charged particles are reflected and accelerated. Thus, thermal electrons gain energy due to multiple reflections between two approaching SLAMS. The second mechanism shows that it is possible to accelerate electrons inside a single SLAMS due to a noncoplanar component of the magnetic field in these structures. Both mechanism are described in the form of test particle calculations, which are supplemented by calculations according to adiabatic theory. The results are discussed for circumstances in the solar corona and in interplanetary space. 相似文献
8.
We propose a new mechanism of a change in the brightness temperature of the ocean due to the contribution from steep mesoscale
waves and estimate the contribution of such waves to the brightness temperature of the ocean. A steep wave is simulated by
an inclined surface. The estimates show that variations in the radio-brightness temperature due to steep irregularities can
reach several kelvins at low grazing angles. For short observation distances and low grazing angles, the brightness temperature
has bursts similar to those observed in the case of backscattering. These bursts occur when breaking waves hit the observation
area.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 43, No. 3, pp. 217–223, March, 2000 相似文献
9.
The generation of the third harmonic of femtosecond laser radiation with a wavelength of 1.24 μm tightly focused into the
bulk of fused silica was simulated numerically for the regime with light intensity of 3 × 1013 W/cm2, which is extreme for solid bodies. The efficiency of third harmonic generation (THG) was found to be restricted to 0.1%
in the regime of plasma formation. This is determined by two competitive processes: a decrease of THG efficiency due to an
increase of wave detuning and an increase of THG efficiency due to a growth of focusing asymmetry. In an isotropic medium,
determination of the threshold of plasma formation by use of the third harmonic signal is shown to be a more sensitive method
as compared with the standard scheme of nonlinear transmittance detection. 相似文献
10.
E. Massoro G. Matt B. Agrinier B. Parlier E. Barouch J. C. Christy R. Comte B. Sacco L. Scarsi T. Mineo G. Agnetta R. Di Raffaele M. Niel P. Mandrou P. von Ballmoos P. Frabel G. Rouaix J. L. Masnou L. Perret G. Gerardi M. Salvati E. Costa 《Il Nuovo Cimento C》1992,15(5):801-809
Summary The FIGARO II (French Italian Gamma-Ray Observatory) experiment has been launched successfully three times: in July 1986 from
Milo (Trapani), in November 1988 from Charleville (Australia) and in July 1990 again from Milo. In the first flight the observational
program was limited to the Crab pulsar PSR0531+21 only because of a telemetry failure: the high sensitivity of FIGARO II allowed
an accurate study of the pulse shape as well as a phase-resolved spectroscopy. It was also possible to evaluate the dispersion
measure of the Crab pulsar at the flight date from the time delay between gamma-ray and radio pulses. The major results of
the second flight were a stringent upper limit to the low-energy gamma-ray flux from PSR 0833-45 (Vela pulsar)—well below
the detection claimed by the UCR group —and the observation of a strong emission in the 0.511 MeV annihilation line from the
inner region of our Galaxy. The data acquired in the third flight are still under analysis, but preliminary results suggest
changes in the shape of the pulse profile.
Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990. 相似文献
11.
We study the effect of striction plasma density disturbances on the generation intensity of longitudional cold and plasma
oscillations due to polarization of the magnetic field-aligned ionospheric plasma irregularities with δNo<0 by a powerful radio wave. It is assumed that the plasma density level inside the irregularity intersects the upper-hybrid
resonance level, in the vicinity of which the cold oscillations excited directly by a powerful radio wave are transformed
to shorter-wave plasma oscillations. We consider the short plasma wave limit to reduce the problem to a system of two coupled
equations for the cold wave induction and plasma wave electric field. The first equation is supplemented by a local source
equal to the integral of the plasma wave electric field in the resonance region. The second equation involves the cold wave
induction at the resonance point and describes the electric field of interacting waves in the resonance vicinity. We use simplifications
connected with the small absorption of plasma waves propagating inside the irregularity and weak radiation of these waves
outside the irregularity. These conditions correspond to the generation of eigenmodes of plasma oscillations trapped in the
irregularity. We have obtained a resonance-type nonlinear equation for the electric field intensity (or energy flux) of eigenmode
plasma waves with allowance for striction disturbances of the plasma density profile in the resonance region. It is shown
that the striction expulsion of plasma is responsible for the occurrence of coefficients describing the change in the intensity
of excitation and radiation of plasma waves at the irregularity boundary. Such an expulsion leads to variations of the efficient
generation band of plasma eigenmodes with the total phase increment of the wave in the irregularity. It also leads to a change
in the phase shift of the plasma wave reflected from the resonance. These coefficients and the nonlinear phase shift are expressed
in terms of real wave functions of the nonlinear Airy equation which describes the electric field of the excited waves in
the resonance vicinity when the dissipation is absent.
Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences, Troitsk, Moscow region,
Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 3, pp. 270–297, March, 1998. 相似文献
12.
N. V. Bakhmet’eva G. I. Grigor’ev A. V. Tolmacheva 《Radiophysics and Quantum Electronics》2011,53(11):623-637
We present the results of measuring characteristics of the ionosphere and neutral atmosphere by the method of resonant scattering
of radio waves by artificial periodic irregularities of the ionospheric plasma in the altitude range 90–120 km. It is shown
that the altitude–time variations of the measured characteristics are in many respects stipulated by the propagation of atmospheric
waves. Hydrodynamic instabilities in the mesosphere—lower thermosphere are analyzed. Criteria of development of different-type
instabilities are presented. Contribution of different processes to the dynamics of the medium is estimated on the basis of
the measurement results. 相似文献
13.
V. P. Uryadov G. G. Vertogradov V. G. Vertogradov S. V. Kubatko A. A. Ponyatov Yu. N. Cherkashin I. V. Krasheninnikov V. A. Valov G. P. Komrakov A. V. Makarov D. V. Bredikhin 《Radiophysics and Quantum Electronics》2009,52(4):241-251
We describe the operation of an ionosonde/position finder with chirp modulation of the signal. The first results of measuring
the characteristics of short-wave radio signals scattered by artificial small-scale inhomogeneities, which were obtained by
means of an ionosonde/position finder on the IZMIRAN—“SURA”—Rostov-on-Don path are presented. It was found that under certain
ionospheric conditions, the angular and frequency selection of the scattered signals take place, in which case the signals
are observed simultaneously in several frequency intervals (mainly, in three, namely, 6–9.5 MHz, 10–12 MHz, and 15–18 MHz)
with different angles of incidence of radio waves in the vertical plane. In this case, the incidence angles were 20◦–35◦,
18◦–32◦, and 10◦–20◦ from the horizon for the first, second, and third frequency interval, respectively. Ionograms of oblique
sounding were modeled allowing for the scattering of radio waves by artificial small-scale inhomogeneities. It is shown that
at frequencies from 10 to 12 MHz, aspect conditions are fulfilled for the signals ducting along the high-angle beam (Pedersen
mode). At frequencies 15–18 MHz (higher than the maximum observable frequency of the forward signal on the path IZMIRAN—Rostov-on-Don),
aspect scattering conditions are fulfilled for the signals incident on a scattering area in the ascending part of the trajectory.
At low frequencies 6–9.5 MHz (below the maximum observed frequency of the forward signal on the IZMIRAN—Rostov-on-Don path),
the observable additional signals are caused by the scattering of radio waves by artificial inhomogeneities with subsequent
relfection of the scattered signal from the Earth on the “SURA”—Rostov-on-Don path.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 52, No. 4, pp. 267–278, April 2009. 相似文献
14.
K. Kalinowski V. Roppo T. ?ukasiewicz M. ?wirkowicz Y. Sheng W. Krolikowski 《Applied physics. B, Lasers and optics》2012,109(4):557-566
We theoretically study the parametric wave interaction in nonlinear optical media with randomized distribution of the quadratic nonlinearity $\chi ^{(2)}$ . In particular, we discuss the properties of second and cascaded third harmonic generation. We derive analytical formulas describing emission properties of such harmonics in the presence of $\chi ^{(2)}$ disorder and show that the latter process is governed by the characteristics of the constituent processes, i.e. second harmonic generation and sum frequency mixing. We demonstrate the role of randomness on various second and third harmonic generation regimes such as Raman?CNath and ?erenkov nonlinear diffraction. We show that the randomness-induced incoherence in the wave interaction leads to deterioration of conversion efficiency and angular spreading of harmonic generated in the processes relying on transverse phase matching such as Raman?CNath interaction. On the other hand, the ?erenkov frequency generation is basically insensitive to the domain randomness. 相似文献
15.
In this paper, the interactions of three types of adjacent combined solitary waves, which are conveniently called Types I, II, and III combined solitary wave, respectively, are numerically investigated. The results show that their interactions exhibit quite different properties. For Type I combined solitary waves, the interaction is quite weaker than that of dark solitons for the standard nonlinear Schrödinger (NLS) equation. Interestingly, the interaction can be well suppressed when they are reduced to the pure dark ones. But for Type II combined solitary waves, the interaction is much stronger than those of Types I and III combined solitary waves and is very difficult to be suppressed. Surprisingly, two adjacent Type III combined solitary waves, both brightlike and darklike ones, hardly interplay each other. These results imply that Type I pure dark solitary waves and Type III combined solitary waves may be regarded as appropriate candidates for information carriers. In addition, the propagation of pulse trains composed of combined solitary waves is investigated. 相似文献
16.
17.
A. V. Kostrov V. V. Nazarov M. V. Starodubtsev 《Radiophysics and Quantum Electronics》2007,50(8):665-678
We present the results of the laboratory modeling of physical processes occurring in the ionosphere during active experiments
on the ionospheric modificaton by powerful radio emission. The process of nonuniform thermo-diffusion of a magnetoplasma due
to local electron heating is studied under the conditions modeling the ionospheric F layer. It is revealed by direct measurements
that thermo-diffusion and diffusion are accompanied by excitation of macroscopic eddy currents. In this case, electrons and
ions diffuse along and across the magnetic field, respectively, and the eddy current is carried by particles of the background
plasma. As a result, a magnetic-field-aligned density depletion rapidly forms in the plasma. The possibility of trapping and
guided propagation of Langmuir waves in such a plasma inhomogeneity is demonstrated. Conditions are found under which the
wave trapping and the formation of the inhomogeneity occur in a self-consistent regime, i.e., Langmuir waves are trapped in
a small-scale inhomogeneity which, in turn, is formed due to local plasma heating by the field of the trapped waves. Such
nonlinear wave trapping takes place only above a certain threshold, which significantly increases in the vicinity of gyroharmonics.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 8, pp. 731–746, August 2007. 相似文献
18.
V. P. Burmaka I. F. Domnin V. P. Uryadov L. F. Chernogor 《Radiophysics and Quantum Electronics》2009,52(11):774-795
We describe the results of using the incoherent scatter technique to observe time-altitude variations in regular parameters
of the ionospheric plasma and wave disturbances, which accompanied periodic modification of the near-Earth plasma by radio
waves emitted by the “Sura” facility. A distinctive feature of the experiments was that the processes in the ionosphere were
diagnosed at a distance of about 1000 km from the facility. It was found that the spectrum composition of wave disturbances
in the electron density was changing noticeably during the active experiment. Quasi-periodic processes in the ionosphere were
observed with a delay of about 40–60 min. The relative amplitude of wave disturbances was equal to 0.02–0.10, and the periods
were equal to 30, 60, 120, and 150–180 min. The observed effect can be explained by the generation and/or amplification of
traveling ionospheric disturbances. The results of theoretical estimations agree well with the observational data. 相似文献
19.
The absorption of a high-energy photon from the external cosmic gamma-ray background in the inner neutron star magnetosphere
triggers the generation of a secondary electron-positron plasma and gives rise to a lightning—a lengthening and simultaneously
expanding plasma tube. It propagates along magnetic fields lines with a velocity close to the speed of light. The high electron-positron
plasma generation rate leads to dynamical screening of the longitudinal electric field that is provided not by charge separation
but by electric current growth in the lightning. The lightning radius is comparable to the polar cap radius of a radio pulsar.
The number of electron-positron pairs produced in the lightning in its lifetime reaches 1028. The density of the forming plasma is comparable to or even higher than that in the polar cap regions of ordinary pulsars.
This suggests that the radio emission from individual lightnings can be observed. Since the formation time of the radio emission
is limited by the lightning lifetime, the possible single short radio bursts may be associated with rotating radio transients
(RRATs). 相似文献
20.
A. I. Sychev 《Thermophysics and Aeromechanics》2009,16(2):259-265
Wave processes in chemically active multicomponent media: liquid — gas bubbles — liquid drops have been studied experimentally.
Existence of detonation waves in multicomponent (bubble-drop) media has been proved. Structure of detonation waves in bubble-drop
and bubble media is qualitatively identical: detonation waves are solitary waves with pulsation profile the pressure behind
which is close in value to the one in unperturbed medium. Propagation velocity of detonation waves in bubble and bubble-drop
media drops with the increase in medium gas phase concentration and with the decrease in carrier liquid viscosity. Presence
of liquid drops decreases detonation wave velocity compared with bubble medium that does not contain liquid drops. Detonation
wave propagation in multicomponent media causes gas bubbles fragmentation as well as fragmentation of individual liquid drops.
The work was financially supported by the Russian Foundation for Basic Research (Grant No. 04-03-33106). 相似文献