共查询到20条相似文献,搜索用时 31 毫秒
1.
A solution to the Sommerfeld problem of the far (in terms of wavelengths) field of a vertical electrical dipole placed at the interface between two media has been found. The characteristics of a surface electromagnetic wave that propagates over a medium with highly inductive surface impedance δ have been determined. The spatial characteristics of the wave are expressed through the real and imaginary parts of impedance δ. It has been proved that the surface electromagnetic wave is the major contributor to the electromagnetic field of the ground wave in the case of highly inductive radio paths. 相似文献
2.
A. V. Men’ 《Radiophysics and Quantum Electronics》2008,51(2):83-100
We present universal formulas for spectral characteristics of cosmic radio sources of synchrotron radiation upon the presence
of spectral density maxima at certain frequencies (spectra with negative curvature) taking into account most typical physical
processes observed in space. On the basis of long-term observations of angular radiation structure of cosmic radio sources
in the decameter wavelength range by the URAN radio interferometer system, we determine most probable physical processes resulting
in spectra with extremum values for several quasars, radio galaxies, and their separate components. On the basis of these
data, we estimate some parameters of cosmic medium, magnetic field, and angular sizes of compact radio sources and their components.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 2, pp. 91–110, February 2008. 相似文献
3.
4.
A. D. Filonenko 《JETP Letters》2009,89(8):381-384
The effect of the environment on the results of measuring the radio radiation spectrum is considered in the experimental simulation of the cascade shower by a high-energy γ-ray beam in a dense medium. The calculation shows that the character of the measured energy spectrum depends on the location of the receiving antenna with respect to the shower axis. 相似文献
5.
S. E. Savotchenko 《Journal of Experimental and Theoretical Physics》2018,126(2):284-292
It has been shown that localized and semi-localized stationary states exist near a thin structured defect layer between a linear medium and a Kerr nonlinear medium. Localized states are described by a monotonically decreasing amplitude of the field on the both sides of the interface between the media. Semilocalized states are characterized by the field that has the form of a standing wave in the linear medium and decreases monotonically in the nonlinear medium. Kerr media with self-focusing and defocusing are considered. The proposed model is described by a system of the linear and nonlinear Schrödinger equations with a specific potential simulating a thin structured defect layer. It has been shown that localized and semi-localized states exist in different energy ranges in the case of contact of the linear medium with the self-focusing medium. In the case of contact of the linear medium with the defocusing medium, two types of localized and semi-localized states differing in energy and field profile can exist in different energy ranges. In particular cases, expressions for energies of states of these types have been obtained and conditions of their applicability have been indicated. 相似文献
6.
G. A. Gusev 《Bulletin of the Lebedev Physics Institute》2011,38(1):15-19
It was shown that the effect of plasma production during solid medium ionization by a developing cascade can shield excess-charge radiation in the radio range used for detecting particles at energies higher than 1020 eV. Such a shielding effect is significant in Antarctic ice and is insignificant for lunar regolith. Hence, the LORD experiment on detection of cascades from ultrahigh-energy cosmic rays and neutrinos from circumlunar spacecrafts retains the capability of measurements up to the energies of 1023 eV. 相似文献
7.
E. E. Meshkov 《Journal of Experimental and Theoretical Physics》2018,126(1):126-131
The interface between two media of different densities (contact boundary) moving with an acceleration directed from the less dense medium to the more dense one is unstable (Rayleigh–Taylor instability) [1, 2]. The initial perturbations of the interface grow indefinitely and, as a result, a medium mixing zone growing with time is formed at the interface. The structure of such a mixing zone at gas–gas and gas–liquid interfaces is discussed on the basis of laboratory experiments on shock tubes of various types. It is concluded that the regions of turbulent and laminar flows are combined in the mixing zone. 相似文献
8.
V. S. Malyshevsky G. V. Fomin I. A. Ivanova 《Journal of Experimental and Theoretical Physics》2016,122(2):209-215
The problem of the transition radiation of multicharged ions at the interface between two media and in a thin plate under the charge-exchange conditions has been solved. It has been shown that the processes of pickup (or loss) of electrons by accelerated multicharged ions at the interface between two media significantly increases the yield of transition radiation. 相似文献
9.
A. D. Filonenko 《Journal of Experimental and Theoretical Physics》2012,114(3):392-399
We present the results of our calculation of the radio emission field produced by an electron-photon shower from an ultrahigh-energy
particle under the surface of the Moon. We consider two cases of cascade propagation: the first in the lunar regolith-vacuum
direction at small angles to the interface; and the second in the opposite direction when the particle generates a cascade
almost immediately after it has crossed the vacuum-regolith interface. To calculate the relative energy density of the emission
emerged at the surface, we have used the method of decomposing spherical waves into plane ones. The intensity of the refracted
waves for high frequencies has been found to depend strongly on the shower inclination angle. 相似文献
10.
G. A. Gusev 《Bulletin of the Lebedev Physics Institute》2012,39(4):124-129
It is shown that the effect of the formation of electron-hole plasma during ionization of a solid mediumby a cascade developing
in it can shield charge-excess Cherenkov radiation in the radio range used for detecting particles by radio detectors at energies
above 1020 eV. Such a shielding effect is strong in pure Antarctic ice and is weaker in lunar regolith; hence, the LORD experiment on
the detection of cascades from ultrahigh-energy cosmic rays and neutrinos by circumlunar apparatuses retains the possibility
of detecting particles to energies of ∼3 · 1020 eV. 相似文献
11.
A. D. Filonenko 《JETP Letters》2010,91(9):437-440
It has been shown that small fluctuations of the refractive index of the lunar regolith owing to, e.g., a nonuniform density
distribution, give rise to the loss of the coherence of a Cherenkov radio pulse induced by a cascade shower from an ultrahigh-energy
particle and to a strong decrease in the spectral density of the radio signal. This can be one of the causes of why no events
from ultrahigh-energy cosmic particles on the surface of the moon have been detected. 相似文献
12.
Tim Huege 《Brazilian Journal of Physics》2014,44(5):520-529
Nearly 50 years ago, the first radio signals from cosmic ray air showers were detected. After many successful studies, however, research ceased not even 10 years later. Only a decade ago, the field was revived with the application of powerful digital signal processing techniques. Since then, the detection technique has matured, and we are now in a phase of transition from small-scale experiments accessing energies below 10 18 eV to experiments with a reach for energies beyond 10 19 eV. We have demonstrated that air shower radio signals carry information on both the energy and the mass of the primary particle, and current experiments are in the process of quantifying the precision with which this information can be accessed. All of this rests on solid understanding of the radio emission processes which can be interpreted as a coherent superposition of geomagnetic emission, Askaryan charge-excess radiation, and Cherenkov-like coherence effects arising in the density gradient of the atmosphere. In this article, I highlight the “state of the art” of radio detection of cosmic rays and briefly discuss its perspectives for the next few years. 相似文献
13.
In a cascade three-level atomic system, a parametric study of sub-Poisson or super-Poisson distribution of a stimulated field was performed. By numerical calculation and figures, we investigated the. time evolution of the sub-Poisson distribution of a radiation field. We found that different atomic initial states and different ratios of photon numb& of two radiation fields as well as different ratios of two transitions have a remarkable influence on this distribution. It is interesting to note that under certain conditions, in this cascade structure, there is a high degree of super-Poisson distribution that has not been reported in other structures. We try to explore this anomaly in detail. 相似文献
14.
A. D. Filonenko 《JETP Letters》2014,99(5):250-257
Incoherent radiation of relativistic electrons (positrons) of an extensive air shower in the ultrahigh energy range (~10 GHz) has been studied. The method of the division of an electron track into coherent segments has been used to estimate the power of a radio signal and to determine the radiation pattern. Comparison of the signal with radio noise of an antenna has shown that this radiation can be detected by modern engineering instruments and applied to detect ultrahigh-energy cosmic particles. 相似文献
15.
A. P. Potylitsyn G. A. Naumenko L. G. Sukhikh A. Aryshev M. Shevelev N. Terunuma J. Urakawa 《JETP Letters》2016,104(11):806-810
Transition radiation appearing when a charged particle crosses the interface between two media with different dielectric constants, e.g., a metal–vacuum interface, has been well studied in a wide spectral range. However, primarily, radiation from smooth interfaces has been studied. Transition radiation from conducting gratings (grating transition radiation) is experimentally studied and theoretically analyzed in this work. In this case, it is possible to obtain monochromatic radiation with a tunable frequency depending on the rotation angle of the grating with respect to the electron momentum. Coherent grating transition radiation can be efficiently used as a source of terahertz radiation based on the use of a compact electron accelerator with an energy below 10 MeV and a bunch duration of ≤1 ps. 相似文献
16.
A. D. Filonenko 《Technical Physics》2001,46(3):357-360
The mechanism of radio emission induced by the transient radiation of oppositely charged particles from an extensive air shower
in the geomagnetic field was studied for the first time. For showers with an energy of ∼1022 eV, the electric field strength at a distance of 500 km from the shower axis was found to be 60 μV/mMHz. Such showers attain
their maximum at sea level. The spectral intensity of emission is maximum at frequencies of about 1 MHz (at these frequencies,
the intensity of atmospheric disturbances is minimum). These specific features of radio emission can be used in experiments
for radio detection of high-energy cosmic rays. An experimental setup of such detection is suggested. 相似文献
17.
We consider the transmission of electric dipole radiation through an interface between two dielectrics, for the case of a vertical dipole. Energy flows along the field lines of the Poynting vector, and in the optical near field these field lines are curves (as opposed to optical rays). When the radiation passes through the interface into a thicker medium, the field lines bend to the normal (as rays do), but the transmission angle is not related to the angle of incidence. The redirection of the radiation at the interface is determined by the angle dependence of the transmission coefficient. This near-field redistribution is responsible for the far-field angular power pattern. When the transmission medium is thinner than the embedding medium of the dipole, some energy flows back and forth through the interface in an oscillating fashion. In each area where field lines dip below the interface, an optical vortex appears just above the interface. The centers of these vortices are concentric singular circles around the dipole axis. 相似文献
18.
G. S. Bordonskiy A. A. Gurulev S. D. Krylov A. O. Orlov S. V. Tsyrenzhapov 《Technical Physics》2011,56(9):1314-1319
Polarization measurements are performed for the intensity of microwave radiation at frequencies 13–14 GHz passing through
fresh-water ice cover parallel to the interface between the media. The reasons for the emergence of additional electromagnetic
waves are investigated. In experiments, the formation of two types of additional electromagnetic waves determined by the plane-layer
geometry of the medium (coherent waves) and by the fluidity of ice under the action of mechanical stresses (incoherent waves)
is observed. 相似文献
19.
Gary Koh 《Waves in Random and Complex Media》1992,2(1):39-48
Controlled experiments have been conducted to measure the propagation of synthetically generated pulses in dense random media. The dense media were prepared by embedding spherical dielectric scatterers in a homogeneous background medium: the size and volume fraction of the scatterers were the controlled parameters. A network analyser-based system operating in the frequency domain was used to measure the electric field reflected and transmitted by slab-shaped samples of dense media as the source signal was swept from 26.5 to 40 GHz. An inverse Fourier transform was used to convert the frequency domain response into time domain pulse waveforms. The time domain response was then used to obtain pulse propagation velocity and attenuation in the controlled samples. The experimental results are shown to be in general agreement with dense medium theories. 相似文献
20.
Mirko Boezio 《Brazilian Journal of Physics》2014,44(5):441-449
Cosmic rays are a sample of solar, galactic, and extragalactic matter. Their origin, acceleration mechanisms, and subsequent propagation toward Earth have intrigued scientists since their discovery. These issues can be studied via analysis of the energy spectra and composition of cosmic rays. Protons are the most abundant component of the cosmic radiation, and many experiments have been dedicated to the accurate measurement of their spectra. Complementary information is provided by electrons, which comprise about 1 % of the cosmic radiation. Because of their low mass, electrons experience severe energy losses through synchrotron emission in the galactic magnetic field and inverse Compton scattering of radiation fields. Electrons therefore provide information on the local galactic environment that is not accessible from the study of the cosmic ray nuclei. Antiparticles, namely antiprotons and positrons, are produced in the interaction between cosmic ray nuclei and the interstellar matter. They are therefore intimately linked to the propagation mechanisms of the parent nuclei. Novel sources of primary cosmic ray antiparticles of either astrophysical (e.g., positrons from pulsars) or exotic origin (e.g., annihilation of dark matter particles) may exist. The nature of dark matter is one of the most prominent open questions in science today. An observation of positrons from pulsars would open a new observation window on these sources. Several experiments equipped with state-of-the art detector systems have recently presented results on the energy spectra of electrons, protons, and their antiparticles with a significant improvement in statistics and better control of systematics. The status of the field will be reviewed, with a focus on these recent scientific results. 相似文献