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1.
V. N. Gridnev 《JETP Letters》1999,69(7):546-550
It is shown that the contribution of low-frequency excitations with characteristic energy ℏω
l to T-odd (nonreciprocal) optical effects, including spatial dispersion effects, at optical frequencies ω≫ω
l can be calculated in the zeroth-order approximation with respect to the parameter ω
l/ω. This greatly simplifies their analysis. Some of these effects are found to be frequency independent in the spectral regions
where the refractive index n(ω)≈ const. It is shown that frequency-independent Faraday rotation can be observed in media with zero magnetization, including
in media with zero microscopic magnetic moment density.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 7, 510–513 (10 April 1999) 相似文献
2.
We study the features of the dispersion curves and field structures of the fundamental axisymmetric mode of nonuniform layered
plasma waveguides in a longitudinal magnetic field. It is shown that the presence of sharp boundaries between layers leads
to the appearance of additional branches of the dispersion curves in the frequency range ω Be < ω < ωUH(0), where ωBe is the electron gyrofrequency and ωUH(0) is the upper-hybrid resonance frequency for the near-axis region of a nonuniform waveguide. The fields of eigenmodes corresponding
to these branches comprise resonance structures near the sharp plasma-density variation at which the upper-hybrid resonance
conditions are satisfied and plasma waves are excited. The frequency interval of such a branch is limited by the resonant
frequencies of the neighboring uniform layers. It turns out that in the case of a strong magnetic field ({ie392-01}, where
ωp is the plasma frequency having the value {ie392-02} in the near-axis region of a nonuniform waveguide), the fundamental-mode
field is localized in the near-axis region of a nonuniform waveguide, whereas in the opposite case {ie392-03}, the maximum
wave fields are localized in either the upper-hybrid resonance region or the outer (near-boundary) layer of the waveguide
if there is no resonance region. It is found that the whistler (helicon) contribution to the field structure of the fundamental
axisymmetric mode is very small for narrow nonuniform waveguides (b < λ0, where b is the waveguide radius and λ0 is the wavelength in free space) if the plasma density on the axis is high compared with the cutoff density {ie392-04}. We
present one of the possible explanations for the effect of narrowing of the plasma channel of a high-frequency whistler-range
discharge with distance from a source in the increasing magnetic field.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 5, pp. 434–446, May 2008. 相似文献
3.
The return current induced in a plasma by a relativisitc electron beam generates a new electron-ion two-stream instability
(return current instability). Although the effect of these currents on the beam-plasma e-e instability is negligible, there
exists a range of wave numbers which is unstable only to return current (RC) instability and not to e-e instability. The electromagnetic
waves propagating along the direction of the external magnetic field, in which the plasma is immersed, are stabilized by these
currents but the e.m. waves with frequencies,ω
2≪Ω
e
2
≪ω
pe
2
(Ω
e andω
pe being cyclotron and plasma frequency for the electrons of the plasma respectively) propagating transverse to the magnetic
field get destabilized. Heuristic estimates of plasma heating, due to RC instability and due to decay of ion-acoustic turbulence
generated by the return current, are made. The fastest time scale on which the return current delivers energy to the plasma
due to the scattering of ion-sound waves by the electrons can be ∼ω
pi
−1
(ω
pi being the plasma frequency for the ions). 相似文献
4.
S. N. Molotkov 《JETP Letters》2010,91(12):693-699
The calculations are reported indicating that the transmission of information through a medium with the frequency dispersion
of the refractive index n(ω), where the group velocity is higher than the speed of light in vacuum, always occurs exactly with the speed of light in vacuum. This result is valid for any functional dependence n(ω). 相似文献
5.
Possible use of a gas-discharge plasma in an oscillating field to modulate electromagnetic radiation
The conditions for resonance and signal cutoff are determined from the dispersion relation for the complex refractive index for a plane electromagnetic wave propagating in a gas-discharge plasma when a magnetic field H = H0 + H1ejt is imposed on the plasma. The refractive index and absorption are calculated for circularly polarized waves as functions of the alternating magnetic field with p, b, andv as parameters. Possible observation of modulation of the transmitted signal is demonstrated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 94–99, April, 1971. 相似文献
6.
A new mechanism of a “Coulomb explosion,” where ions are accelerated by the electric field separating charges at the magnetic
Debye radius r
B∼B/4πen
e, is proposed on the basis of a nonquasineutral model of electronic vortices in a magnetic field. It is shown by means of
numerical calculations that in the process of acceleration of the ions a collisionless shock wave, whose front has an effective
width of the order of δ∼r
B, determined by the breakdown of quasineutrality, is formed in a time of the order of ω
pi
−1
, where ωpi is the ion plasma frequency. The origin of such explosive dynamics is the formation of “holes” in the electron density at
characteristic times of the order of ω
pe
−1
(ωpe is the electronic plasma frequency) as a result of the generation of electronic vorticity by the Weibel instability of an
electromagnetic wave. Calculations for a laser pulse with intensity J∼6×1018 W/cm2 show that the ions expand in the radial direction with velocities up to 3.5×108 cm/s.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 10, 669–674 (25 November 1999) 相似文献
7.
R.K. Varma 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(2):211-218
It has been shown earlier [3,6] that matter waves which are known to lie typically in the range of a few angstrom, can also
manifest in the macrodomain with a wave length of a few centimeters, for electrons propagating along a magnetic field. This
followed from the predictions of a probability amplitude theory by the author [1,2] in the classical macrodomain of the dynamics
of charged particles in a magnetic field. It is shown in this paper that this case constitutes only a special case of a generic
situation whereby composite systems such as atoms and molecules in their highly excited internal states, can exhibit matter
wave manifestation in macro and mesodomains, in one-dimensional scattering. The wave length of these waves is determined,
not by the mass of the particle as in the case of the de Broglie wave, but by the frequency ω, of the classical orbital motion
of the internal state in the correspondence limit, and is given by a nonquantal expression, λ = 2πv/ω, v being the velocity of the particle. For the electrons in a magnetic field the frequency corresponds to the gyrofrequency,
Ω and the nonquantal wave length is given by λ = 2πv
|| /Ω; v
|| being the velocity of electrons along the magnetic field.
Received 29 September 2001 / Received in final form 23 May 2002 Published online 19 July 2002 相似文献
8.
Chandu Venugopal 《Pramana》1987,28(2):181-193
A dispersion relation for the near perpendicular propagation of the electromagnetic ion cyclotron wave has been derived in
a fusion plasma that has deuterium as a majority species, hydrogen as a minority species and fully ionized oxygen as an impurity
constituent; all being modelled by loss cone distribution functions. The wave has a frequencyω around the deuterium ion gyrofrequency-ΩD and a wavelength much longer than its Larmor radiusγ
LD(k
⊥
γ
LD<1); the plasma itself being characterized by large ion plasma frequencies (ω
PD
2
>Ω
D
2
). Two modes, a low frequency (LF) and a high frequency (HF) mode of opposite electrical energy can propagate in the plasma;
the instabilities that arise are thus due to an interaction of modes of opposite energies. We find that while hydrogen tends
to destabilize the plasma, the impurity oxygen ions have the reverse effect. Also the plasma is most stable when the ratios
of the perpendicular components of oxygen-to-deuterium and hydrogen-to-deuterium temperatures are kept low. Detailed studies
of the wave propagation characteristics and energy reveal the close resemblance of a loss cone plasma containing oxygen to
a stable Maxwellian plasma in regard to wave stability, propagation and energy. 相似文献
9.
Thermodynamically stable vortex—antivortex structures in a quasi-twodimensional superconductor in a tilted magnetic field
are predicted. For this geometry, both orbital and spin pair-breaking effects exist, with their relative strength depending
on the tilt angle θ. The spectrum of possible states contains the ordinary vortex state (for large θ) and the Fulde-Ferrell-Larkin-Ovchinnikov
(FFLO) state (for θ = 0) as limits. The quasi-classical equations are solved nearH
c2 for arbitrary θ and it is shown that stable states with co-existing vortices and antivortices exist in a small interval close
to θ= 0. The results are compared with recent predictions of antivortices in mesoscopic samples. 相似文献
10.
The dispersion relation of electromagnetic waves in the presence of magnetic monopoles of electron mass in a uniform magnetic
field is obtained. The waves of the frequencyω in the range ωϱi<Ωi<ω<Ω
e
<ωϱa are analysed. It is shown that the monopole charges lead to observable effects. Finally, the results are applied to a typical
pulsar. 相似文献
11.
A Gaussian whistler pulse is shown to cause ponderomotive acceleration of electrons in a plasma when the peak whistler amplitude
exceeds a threshold value and the whistler frequency is greater than half the cyclotron frequency, ω>ω
c
/2. The threshold amplitude decreases with the ratio of plasma frequency to electron cyclotron frequency, ω
p
/ω
c
. However, above the threshold amplitude, the acceleration energy decreases with ω
p
/ω
c
. The electrons gain velocities about twice the group velocity of the whistler. 相似文献
12.
F. Ehlotzky 《Il Nuovo Cimento D》1994,16(5):453-462
Summary We show that for potential scattering of electrons in a bichromatic laser field a Kroll-Watson type of theorem can be derived
in which the scatteringT-matrix element is composed of a renormalized on-shell matrix element for scattering without a field times a generalized Bessel
function factor. The radiation field has two components of frequency ω1 and sω1 (s=2,3,…) and both components are out of phase by an angle ϕ. Our paper is a generalization of earlier investigations which
were performed in the first-order Born approximation. 相似文献
13.
V. G. Dorofeenko 《Russian Physics Journal》1985,28(3):177-182
The two-dimensional (axisymmetric) equilibrium of a modulated electron beam (sequence of bunches) in a magnetoactive plasma under resonance conditions, when the frequency of modulation of the beam
M is close to (less than) the plasma frequency
p, is studied. The field of the collective electrostatic wave, focusing the bunches, is compensated by the thermal repulsion of the beam electrons. Based on the solutions obtained, it is established that the external magnetic field has a twofold effect on the equilibrium beam: first, to a weakening of the radial component of the focusing field because of the appearance of anisotropy in the dielectric permittivity tensor of the plasma and, second, an additional radial focusing of the bunches when they are rotated by the Lorentz force. The regions of the beam and plasma parameters in which one or another of the indicated effects predominates are determined and the conditions for the predominance of magnetic over electrostatic focusing are found.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 3–8, March, 1985.The author thanks V. B. Krasovitskii for proposing the subject and for constant interest in this work. 相似文献
14.
G. N. Kichigin 《Journal of Experimental and Theoretical Physics》2009,109(3):408-416
We consider the problem of cosmic-ray generation through the surfing acceleration of charged particles in relativistic magnetosonic
shock waves (the branch of fast magnetic sound) propagating in magnetized space plasmas. The dependence of the particle surfing
acceleration efficiency on the angle θ
Bn
between the normal to the shock front plane and the magnetic field vector in the plasma upstream of the shock is analyzed
in detail. We show that for angles satisfying the condition χ = βΓ tan θ
Bn
⩾ 1, where β = U/c, Γ = (1 − β)2
−1/2, U is the shock velocity, and c is the speed of light, the particles can theoretically be accelerated through surfing for an unlimited time and can gain
an unlimited energy. For angles satisfying the condition χ < 1, the kinetic energy ℰ of the particles is limited by ℰ = 2mc
2χ2/(1 − χ2) (m is the particle rest mass). Our main conclusion is that the generation of cosmic rays through the surfing acceleration of
particles in the front of a relativistic shock wave for Γ ≫ 1 is also efficient when the angle θ
Bn
is very small, i.e., it differs significantly from a right angle. Estimates for the energies of particles accelerated through
surfing in relativistic jets are provided. 相似文献
15.
16.
Conical refraction, which is due to the renormalization of the elastic moduli by the effective magnetoelastic interaction
and depends on the static magnetic field, has been experimentally observed in an α-Fe2O3 trigonal easy-plane antiferromagnet in addition to the usual internal conical refraction of transverse elastic waves propagating
along the trigonal C
3 axis. It has been shown that the deviation angle θη of the energy flux from the C
3 axis at the internal conical refraction is independent of the magnetic field applied in the basal plane (H ⊥ C
3) and is a constant determined by the ratio of the elastic moduli C
14 and C
44. The deviation angle of the energy flux at the antiferromagnetic conical refraction increases with the magnetic field and
approaches the value θη at large H values. The results are well described by the theory of this phenomenon developed by E.A. Turov and confirm its basic conclusions. 相似文献
17.
18.
The direct component of the electric current induced in graphene placed in a constant magnetic field has been found in the
case where two electromagnetic waves with two mutually perpendicular planes of polarization are normally incident on the surface
of the sample. It has been demonstrated that the direct component of the current along the direction of the electric field
vector of the wave with the frequency ω1 arises only when the ratio between the frequencies of the incident waves is ω1/ω2 = 2 or 1/2. In the latter case, the direct current component appears only in the presence of a magnetic field. 相似文献
19.
The role of low density upflowing field-aligned electron beams (FEBs) on the growth rate of the electron cyclotron waves at
the frequencies ω
r < Ωe, propagating downward in the direction of the Earth’s magnetic field, has been analysed in the auroral region at ω
e/Ωe < 1 where ω
e is the plasma frequency and Ωe is the gyrofrequency. The FEBs with low to high energy (E
b) but with low temperature (T
‖b) have no effect on these waves. The FEBs with E
b < 1 keV and T
‖b (> 1.5 keV) have been found to have significant effect on the growth rate. Analysis has revealed that it is mainly the T
‖b which inhibits the growth rate (magnitude) and the range of frequency (bandwidth) of the instability mainly in the higher
frequency spectrum. The inhibition in the growth rate and bandwidth increases with increase in T
‖b. The FEBs with less E
b (giving drift velocity) reduce growth rate more than the beams with larger E
b. The inhibition of growth rate increases with the increase in the ratio ω
e/Ωe indicating that the beams are more effective at higher altitudes.
相似文献
20.
B. Lalevic N. Fuschillo B. Kuliyev W. Wang 《Applied Physics A: Materials Science & Processing》1974,5(2):127-132
Transport and dielectric properties of polycrystalline CoO films were studied as functions of the applied field, frequency
and temperature. TheI–V plots showed that the Poole-Frenkel field emission mechanism is responsible for conduction at fields>105 V/cm. The ac conductivity σ(ω), the imaginary part of the dielectric constantε
2, and tan δ plots as functions of frequency revealed three dispersion regions. The σ(ω) andε
2 frequency dependence indicates a non-adiabatic hopping of charge carriers at low frequencies and adiabatic hopping at high
frequencies. The activation energy of a dielectric oscillator is 0.15 eV.
Work supported by the Office of Naval Research. 相似文献