The external field effect on transient radiation of an ultrarelativistic particle

An external field determining the law of particle motion was shown to change the intensity of transient radiation in the ultrarelativistic case. The angular and frequency distribution of transient radiation in an external field was obtained. The possibility of determining the energy of an ultrarelativistic particle from the measured azimuthal asymmetry of particle transient radiation in an external field was discussed.     

A quantum correction to radiation theory for a short-magnet system

The radiation pattern is considered for an ultrarelativistic spinless charged particle deflected through a small angle by an external magnetic field. The radiation characteristics are determined up to the first order in the Plank constant. The quantum parameter in the expansion differs substantially from the corresponding quantum parameter in synchrotron radiation theory.Tomsk Polytechnical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 61–65, November, 1993.     

Synchrotron radiation in curved space—time

Synchrotron emission by ultrarelativistic particles moving in a magnetic field in curved space-time is examined by the method of local coordinates. Generally covariant equations are obtained for the radiation spectrum in the classical and quantum cases. It is shown that the relative magnitude of the quantum corrections to the radiation spectrum increases with particle motion near the event horizon in the Kerr metric. The limit of geodesic synchrotron radiation is examined.     

Transition radiation from an ultrarelativistic particle in an external field at grazing emission angles

The effect of an external field on the transition radiation from an ultrarelativistic particle is considered at grazing emission angles. The angular and frequency distribution of transition radiation is found. It is shown that the external field substantially increases the angular asymmetry of transition radiation at grazing emission angles.     

Relativistic laser-matter interaction and relativistic laboratory astrophysics

The paper is devoted to the prospects of using the laser radiation interaction with plasmas in the laboratory relativistic astrophysics context. We discuss the dimensionless parameters characterizing the processes in the laser and astrophysical plasmas and emphisize a similarity between the laser and astrophysical plasmas in the ultrarelativistic energy limit. In particular, we address basic mechanisms of the charged particle acceleration, the collisionless shock wave and magnetic reconnection and vortex dynamics properties relevant to the problem of ultrarelativistic particle acceleration.     

Dependence of diffraction radiation on the energy of an ultrarelativistic particle

The possibility of a strong dependence of the diffraction radiation of an ultrarelativistic charged particle on its Lorentz factor is discussed. It is shown that the distribution of diffraction radiation arising when the ultrarelativistic particle flies parallel to a thin dielectric layer with finite sizes depends strongly on the Lorentz factor of the particle.     

The polarisation of gravitational synchrotron radiation

In the linear approximation we show that the gravitational radiation induced by ultrarelativistic charges, moving in a magnetic field or in the field of a circularly polarised electromagnetic wave does not have the primary linear polarisation contrary to the case of the electromagnetic synchroton radiation.     

Synchrotron radiation and the intrinsic magnetic moment of the electron

Little-studied aspects of the role of the intrinsic magnetic moment including its anomalous part in the synchrotron radiation of ultrarelativistic electrons are examined. The Fourier, transform of the polarization components of the radiation field intensity vector is written in explicit form. The spectral-angular distribution of the radiation power is found, and the terms related to the radiation of the charge and the intrinsic magnetic moment, and to quantum yield effects are determined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 49–52, May, 1990.     

Particle creation by charged black holes

A simple derivation is given for the leading term (n=1) in the Schwinger formula for the pair creation by a constant electric field. The same approach is applied then to the charged particle production by a charged black hole. In this case, as distinct from that of a constant electric field, the probability of the charged particle production depends essentially on the particle energy. The production rate by black holes is found in the nonrelativistic and ultrarelativistic limits. The range of values for the mass and charge of a black hole is indicated where the discussed mechanism of radiation dominates the Hawking one.     

Behavior of the spin of ultrarelativistic electrons in electrostatic fields with axial symmetry

The phenomenon of spin self-orientation of ultrarelativistic electrons in an external axially symmetric focusing electrostatic field is studied. The conditions for the existence of such collective phenomenon are clarified, as well as its nature. The analysis is based upon the Bargman-Michel-Telegdi equation which takes into account the influence on the particle spin of both the external electromagnetic field and the radiation field.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 53–56, September, 1991.     

On the theory of diffraction radiation

A macroscopic theory of diffraction radiation emerging when a charged point particle moves in the vicinity of a perfectly conducting screen is developed. The integral equations derived for radiation fields form the basis for analyzing the similarity and difference of diffraction of electromagnetic radiation and diffraction radiation from a charged particle. It is shown that in the case considered here, the widely used model in which the radiation field can be represented as the field of surface current has more stringent limits of application as compared to the classical theory of diffraction. This considerably restricts the applicability of the results obtained earlier using the double-layer method to only ultrarelativistic energies and to transit angles of particles close to the direction of the normal to the screen surface. The method developed here is used for analyzing familiar problems of diffraction radiation, such as radiation emerging during normal transit of a particle along the axis of a circular aperture in the screen, radiation emitted during oblique transit near a perfectly conducting half-plane, and radiation emitted during oblique transit of a particle through a rectangular slit in an infinitely large screen. In the latter case, the results obtained after the limiting transition to zero width of the slit completely coincide with the theory of transition radiation for arbitrary energies of the particle and its angle of incidence to the screen.     

Boson radiation in a periodic magnetic field

The first correction to the boson radiation intensity is obtained in an arbitrary two-component periodic magnetic field. In the ultrarelativistic case, the quantum correction for a specific kind of potential in which spiral motion is realized will agree with the corresponding expression in the theory of synchrotron radiation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 27–32, September, 1989.The authors are grateful to Prof. V. G. Bagrov for attention to the research.     

Diffraction radiation of a dielectric wedge at the resonance frequency

The diffraction radiation at the frequency that is close to the natural resonance of the medium is considered for a fast charged particle that passes in the vicinity of a dielectric wedge. The dependence of the angular distribution of the diffraction radiation on the angle between the wedge faces and on the energy of the ultrarelativistic particle is analyzed.     

Momentum spread in a relativistic electron beam in an undulator

The motion of the relativistic electron beam in the spatially periodic magnetic field of an undulator has been considered taking into account the effect of the incoherent field of the spontaneous undulator radiation on the motion of the electrons. An expression for the rms momentum of the electrons has been obtained. It has been shown that the momentum spread in the ultrarelativistic electron beam increases in the spontaneous incoherent emission mode. Conditions for the self-amplification of the spontaneous undulator radiation in ultrashort-wavelength free-electron lasers have been discussed.     

Cold neutral plasma in a quantizing magnetic field

The chemical potential of a relativistic and an ultrarelativistic electron gas and the energy of an ultrarelativistic electron gas at T = 0 are expressed analytically as functions of the magnetic field. The possible application of these expressions to the investigation of super-compressed matter in the presence of superstrong magnetic fields is discussed.     

Stability of equilibrium orbits in isochronous ultrarelativistic cyclotron I

The paper deals with an investigation into the equilibrium orbits of charged particles in one variant of the isochronous ultrarelativistic cyclotron, i.e. accelerator with time independent, axially increasing magnetic field and strong focusing for accelerating charged particles at constant orbital time. The author finds phenomena well known from the theory of oscillations of non-linear mechanical systems (in a certain region of the parameters of a magnetic field there exist substantially two equilibrium orbits, while in another region none exist), which have no analogy in other accelerators. A variant of the ultrarelativistic cyclotron with axially scalloped equilibrium orbit is proposed.     

On the connection between the gamma and radio spectra of pulsars

We suggest a model of pulsar radio emission in which a coherent radio emission is excited in a vacuum gap above the polar cap of a neutron star. The pulsar X-ray and gamma radiation is considered as the result of inverse Compton scattering of radio emission by ultrarelativistic electrons accelerated in the gap. The influence of the pulsar magnetic field on the inverse Compton scattering is taken into account. The relationship between the radio and gamma spectra has been found in this model.     

Observable acceleration of jets by a Kerr black hole

In the framework of a model based on the gravitational field of the Kerr black hole, we turn to investigate the kinematic behavior of extragalactic jets. We analytically calculate the observable velocities and accelerations along any geodesic. Then, by numerical calculations, we apply our results to a geodesic, typical of the M87 jet, and probe our results by confrontation to recent observations. A transition from non-relativistic to ultrarelativistic speeds at subparsec scale is highlighted. This transition comes sooner and more abruptly than in models based on magnetic paradigm, which indicates that we need a weaker magnetic field to explain observed synchrotron radiation. We attribute the ejection phenomenon to the repulsive effect of the gravitomagnetic Kerr field.     

Ultrarelativistic electron optics in a weak magnetic field

Within an unprecedented analytical formulation, we find an approximate relationship for the ultrarelativistic velocity of electrons in the presence of a weak, time-independent and uniform magnetic field acting perpendicularly to the trajectory of the electrons. We also determine the corresponding velocity quantum operator whose eigenvalues are also determined as well as their corresponding Landau states. In addition, the corresponding synchrotron radiation losses are calculated.     

Transient radiation in an anisotropic magnetodielectric plate in a waveguide

We have considered transient radiation of a charged particle in an anisotropic magnetodielectric plate placed into a regular waveguide. It is assumed that the charged particle passes through the plate moving at a constant velocity perpendicularly to the waveguide axis. Wave equations and analytical expressions for transverse electric (TE) and transverse magnetic (TM) fields in different regions of the waveguide have been obtained. Energies of transient radiation of the moving particle have been calculated. The properties of transient radiation and Vavilov–Cherenkov radiation have been analyzed for the case of a rectangular waveguide. Energies of transient radiation have been calculated for the case of a “thin” plate in the waveguide, when the wavelength in the plate is much greater than the length of the plate.