Electromagnetic radiation recoil of a system ofN-charged particles

We give the radiation of anN-charged particles system associated with the succeeding terms in the expansion in the inverse powers of the velocity of light of the four vector force on the material system in a slow motion. We investigate the conditions under which theN-charged particles system may recoil while emitting electromagnetic radiation. Furthermore, the lowest-order secular effects in the radiation arise from dipole and quadrupole radiations exactly as it is expected from the classical theory.     

On the energy density of the cosmic microwave background

Starting from the assumption that the radiation source at the origin of the cosmic microwave background (CMB) could not have a luminosity larger than the maximum energy in ordinary matter divided by the minimum time allowed by causality, one arrives at an expression that gives the energy density of CMB as a function of the main cosmological parameters. Also, by defining a radiation charge as the hypothetical charge that opposes the congregation of a cloud of particles around a source of electromagnetic radiation, on arrives at another expression for the energy density of CMB that agrees exactly with the measured value for a value of the Hubble constant equal to 72.09 km s⁻¹ Mpc⁻¹. Both expressions are independent of the redshift.     

Dust particle in the solar gravitational and electromagnetic fields

The action of the solar electromagnetic radiation (in the form of the Poynting-Robertson effect) on the motion of interplanetary dust particle in the gravitational field of the Sun is discussed from the theoretical point of view. Results are presented to all orders inv/c (c - speed of light,v -orbital velocity of the particle) - general relativistic formula is presented.     

Vlasov – Maxwell,Self-consistent Electromagnetic Wave Emission Simulations in the Solar Corona

1.5D Vlasov – Maxwell simulations are employed to model electromagnetic emission generation in a fully self-consistent plasma kinetic model for the first time in the context of solar physics. The simulations mimic the plasma emission mechanism and Larmor-drift instability in a plasma thread that connects the Sun to Earth with the spatial scales compressed appropriately. The effects of spatial density gradients on the generation of electromagnetic radiation are investigated. It is shown that a 1.5D inhomogeneous plasma with a uniform background magnetic field directed transverse to the density gradient is aperiodically unstable to the Larmor-drift instability. The latter results in a novel effect of generation of electromagnetic emission at plasma frequency. The generated perturbations consist of two parts: i) non-escaping (trapped) Langmuir type oscillations, which are localised in the regions of density inhomogeneity, and are highly filamentary, with the period of appearance of the filaments close to electron plasma frequency in the dense regions; and ii) escaping electromagnetic radiation with phase speeds close to the speed of light. When the density gradient is removed (i.e. when plasma becomes stable to the Larmor-drift instability) and a low density super-thermal, hot beam is injected along the domain, in the direction perpendicular to the magnetic field, the plasma emission mechanism generates non-escaping Langmuir type oscillations, which in turn generate escaping electromagnetic radiation. It is found that in the spatial location where the beam is injected, standing waves, oscillating at the plasma frequency, are excited. These can be used to interpret the horizontal strips (the narrow-band line emission) observed in some dynamical spectra. Predictions of quasilinear theory are: i) the electron free streaming and ii) the long relaxation time of the beam, in accord with the analytic expressions. These are corroborated via direct, fully-kinetic simulation. Finally, the interplay of the Larmor-drift instability and plasma emission mechanism is studied by considering a dense electron beam in the Larmor-drift unstable (inhomogeneous) plasma. The latter case enables one to study the deviations from the quasilinear theory.     

The cosmic microwave background radiation in a non-expanding universe

During the nineteenth century, it was common for physicists to believe in the existence of a material vacuum composed of an incompressible fluid that fills the whole universe. This fluid was called the aether. Its original purpose was to provide an elastic tenuous medium for light propagation through space. Although it is well understood today that no such medium is needed for light propagation, the existence of a cosmic aether medium in space is still possible and its physical properties can be understood on models of cosmology that have nothing to do with Big-Bang cosmology. It is possible that electromagnetic radiation emitted by the cosmic aether medium has already been detected. The low-frequency electromagnetic radiation emitted by the aether is called the cosmic microwave background radiation. The present study outlines a model for an aether medium that explains the genesis of the microwave background radiation in a closed static (nonexpanding) universe. It is shown that the spectrum of the microwave background radiation is a perfect blackbody with a temperature T _rad=2.77 K in harmony with the perfect cosmological principle. It is further shown that the aether medium is opaque at radio and microwave frequencies. This particular feature of the model does not contradict any observations regarding the existence of distant radio galaxies and quasars.     

Plane of polarization rotation induced by a non-Minkowskian spacetime

Fermat's principle has been used to derive expressions for the curvature and torsion of the path of the electromagnetic radiation in a medium of refractive indexn (= function of space coordinates). Levi-Civita's notion of parallelism further, in conjunction with Brill's results (cf. reference in text) have enabled the derivation (1) of Einstein's formula for the deflection of light, and (2) an expression for the rotation of the plane of polarization, an entirely general relativistic effect, unaccountable in Newtonian physics. Finally, the idea is put forward that the observed rotation of polarization in pulsars might be a purely general relativistic effect due to the non-Minkowskian geometry around them.     

Search for constraints on Lorentz violation parameters by studying the polarization of afterglows from high-energy gamma-ray bursts

The birefringence of electromagnetic radiation from gamma-ray burst (GRB) afterglows due to the Lorentz violation (LV) of spacetime has been calculated. The dependence of this effect on the radiation wavelength and redshift z in the ΛCDM model of the Universe has been established. It is shown that polarization tests for GRB afterglows can be invoked to measure the LV parameters. LV causes oscillations in the parameters of the afterglow spectrum that can be in the ultraviolet spectral range and will depend significantly on redshift z. This can facilitate the recording of LV for an electromagnetic field and can lower significantly the energy threshold of its detection.     

Observational signature of a wind bubble environment for double neutron star mergers

During the in-spiral stage of a compact binary, a wind bubble could be blown into the interstellar medium, if electromagnetic radiation due to the binary orbital motion is strong enough. Therefore, shortduration gamma-ray bursts(SGRBs) due to double neutron star mergers would in principle happen in a wind bubble environment, which can influence the propagation of the SGRB jet and consequent afterglow emission. By calculating the dynamics and synchrotron radiation of the jet-driven external shock, we reveal that an abrupt jump could appear in the afterglow light curves of SGRBs and the observational time of the jump is dependent on the viewing angle. This light curve jump provides an observational signature to constrain the radius of the wind bubble and thus the power of the electromagnetic radiation of the binary,by combining with gravitational wave detection.     

On the generation of modified low‐frequency Farley‐Buneman waves in the solar atmosphere

The possibility of the excitation of Farley‐Buneman turbulence in the solar atmosphere is examined. It is found that the conditions for the generation of the modified Farley‐Buneman instability can be realized in the chromosphere of the Sun 1000 km above the photosphere. While usual Farley‐Buneman waves studied in relation to the Earth's ionosphere are almost electrostatic, the modified Farley‐Buneman waves in the solar atmosphere are electromagnetic ones. This means, that not only the potential electric field caused by the charge distribution, but also the perturbations of the magnetic field and the circularly‐polarized electric field are essential. Although the physical pictures of usual and modified Farley‐Buneman waves are different, their dispersion equations are almost the same. However, the increment of the modified Farley‐Buneman waves is varied by additional electromagnetic effects. It is demonstrated that electromagnetic effects hinder a Farley‐Buneman instability in occurring while ξ < 1, where ξ is the square of the ratio of ion plasma frequency times ion‐neutral frequency to ion‐cyclotron frequency times wave number times speed of light in vacuum. Under the condition ξ > 1, no Farley‐Buneman disturbances appear at all. In weakly‐ionized solar regions, the modified (ξ < 1) and also the usual (ξ ≪ 1) Farley‐Buneman turbulence could make “electromagnetic” contributions to the process of energy dissipation of nonstationary streams of neutral gases. Besides, they may modify the low‐frequency acoustic noise. It seems that the modified Farley‐Buneman turbulence contributes to the sporadic radiation of the Sun. It is possible, that such an effect takes not only place in the chromosphere of the Sun, but also in the atmospheres of other stars.     

Electromagnetic radiation from line sources interacting with a moving magnetoplasma slab backed by a finitely conducting medium

The problem of electromagnetic radiation from electric and magnetic line sources interacting with a moving magnetoplasma slab backed by a finitely conducting medium is treated. The local magnetostatic field is aligned parallel with the line source and is perpendicular to the direction of slab motion. For the configuration, theE andH modes are excited independently by a magnetic and an electric line source respectively. Expressions for the far zone radiation fields and the radiation pattern have been obtained for both the line sources. It is found that the radiation due to an electric line source is not affected by the presence of a static magnetic field and the motion of the slab medium. Numerical results for the radiation pattern referring to both the line sources have been presented for a wide range of parameters characterizing the finite magnetostatic field, the conductivity of the medium backing the plasma, the thickness of the slab and the location of the line source.     

Radio emission of fast cosmic ions

It is usually assumed that the ions of cosmic rays contribute nothing to the observable electromagnetic radiation. However, this is true only when these ions are moving in a vacuum or a quiet (nonturbulent) plasma. In the case of fast ions in a turbulent plasma, there is an effective nonlinear mechanism of radiation which is discussed in this paper. The fast ion (relativistic or nonrelativistic) moving in the plasma creates a polarization cloud around itself which also moves with the particles. The turbulent plasma waves may scatter on the moving electric field of this polarization cloud. In the process of this scattering an electromagnetic wave with frequency (2.7) is generated. Let ₁ and k₁ be the frequency and wave vector of turbulent plasma waves,V is the velocity of the ion, and is the angle between the wave vector of electromagnetic radiation and the direction of the ion velocity. The method of calculating the probability of the conversion of plasma waves (k₁) into electromagnetic waves (k) by scattering on an ion with velocityV is described in detal in Section 2 (Equation (2.14)).The spectral coefficients of spontaneous radiation in the case of scattering of plasma waves on polarization clouds created by fast nonrelativistic ions are given in (3.6) for an ion energy distribution function (3.4) and in (3.8) for more general evaluations. The Equations (3.9)–(3.13) describe the spectral coefficients of spontaneous emission for different modes of plasma turbulence (Langmuir (3.9), electron cyclotron in a weak (3.10) or strong (3.11) magnetic field and ion acoustic (3.12)–(3.13) waves). The coefficients of reabsorption or induced emission are given by Equations (3.14) and (3.16)–(3.19). There is a maser effect in the case of scattering of plasma waves on a stream of ions. The effective temperature of the spontaneous emission is given by Equation (3.15). The spectral coefficients of radiation due to scattering of plasma waves on relativistic ions are calculated in the same manner (Equations (4.14)–(4.15)). The total energy loss due to this radiation is given in Equations (4.23)–(4.25). The coefficients of induced emission are given in (4.26)–(4.28).The results are discussed in Section 5. It is shown that the loss of energy by nonlinear plasma radiation is much smaller than the ionization loss. However, the coefficients of synchrotron radiation of electrons and nonlinear radiation of ions under cosmic conditions may be comparable in the case of a weak magnetic field and fairly low frequencies (5.5)–(5.6). Usually the spectrum of nonlinear plasma radiation is steeper than in the case of synchroton radiation. Equation (5.10) gives the condition for nonlinear radiation to prevail over thermal radiation.Translated by D. F. Smith.     

On the wave mode of subsecond pulses in the cm-range

In this paper we determined the wave mode of subsecond pulses (SSP). We used data on pulses with a degree of polarization over 30%, with the sources located at −60 to +60 deg from the central meridian, for the period 2000–2002. The superposition of SSRT radio maps and MDI magnetograms has shown that radio SSP sources are typically located near the polarity inversion line of the active region magnetic field. Such an arrangement indicates that SSP sources are located at the tops of magnetic loops. The ordinary mode of electromagnetic radiation is recorded in SSP sources located from the inversion line by no less than about 10 arc sec.     

Electromagnetic radiation from line sources interacting with a moving uniaxial dielectric or plasma half-space

The problem of electromagnetic radiation from electric and magnetic line sources interacting with a moving uniaxially anisotropic dielectric or plasma half-space is treated. The anisotropy of the plasma is due to an infinitely strong magnetizing field impressedparallel to the motion of plasma. The line source is oriented normal to the direction of medium motion. TheE and theH modes are excited independently in the medium by the magnetic and the electric line sources, respectively. Invoking the saddle-point method of integration, the far-zone radiation field and the radiation pattern are obtained for both line sources. It is found that the radiation from an electric line source is not affected by the anisotropy of the moving medium and that a magnetic line source invacuum has finite components of radiation in directions which are parallel and antiparallel to the direction of motion, for the case of a uniaxial plasma in contrast to the results for a uniaxial dielectric. Numerical results for the far-zone radiation pattern, referring to a magnetic line source, are presented for several values of parameters characterizing the non-dimensional velocity, the anisotropy of the medium, the electron-plasma density and the location of the line source.     

Planck’s law and the light quantum hypothesis

The phase space of a light quantum in a given volume is subdivided into “cells” of magnitudeh ³. The number of possible distributions of the light quanta of a macroscopically defined radiation over these cells gives the entropy and with it all thermodynamic properties of the radiation.     

On a possible model of the object Cyg X-3

According to the proposed model of the Cyg X-3, it should be recognized as a binary system consisting of a pulsar and an usual star. The plasma with the frozen-in field flows out from the star. The electromagnetic continuous spectrum in the range from radio to gamma radiation owes its origin to the interaction of electrons accelerated by a pulsar with the magnetic field of the stream. The influence of the inverse Compton effect on the spectral distribution of radiation has been considered by the numerical calculations of a system of kinetic equations. The calculations show remarkable agreement with the measurements, if the particle energy spectrum is expressed as dN/dE=AE ^–2.2. The lower limit of the accelerated particle energy equals approximately 10^–2 erg.The situation of the peak of gamma-quantum radiation of very high energy in respect to the minimum in the X-ray radiation can be explained in terms of the suggested model.     

Coulomb-trapped particles in the electromagnetic fields of an oblique magnetic rotator

An oblique, rotating magnetized sphere emits electromagnetic waves which, for large magnetization, can quickly accelerate charged particles to very high energies. A central, attractive Coulomb force can trap particles in the region beyond the light cylinder by balancing the accelerating influence of the radiation on the particles. We sample some of the particle orbits possible under these dynamical conditions. A general feature of these orbits is that non-interacting particles started with random initial conditions in the domain of attraction of these orbits will arrange themselves on a curve corotating with the axis of magnetization. Such particle configurations can be a source of pulsed radiation. In the idealized case of no interparticle interactions the spectral index for the radiation emitted by one frequently occurring configuration is found to be –2/3, for emission from radio to -ray frequencies. The dynamical conditions in this simple model closely match those prevalent in outer pulsar magnetospheres, making it possible that part of the radiation from pulsars is emitted by trapped plasma in the region beyond the light cylinder.     

The maximal photon mean free path sphere and the observable universe

The objective of this paper is to draw attention to the close similarity between the observable universe and the photon mean free path sphere. It is hoped that by analyzing in depth this apparent connection one will be able to explain why our present epoch appears to have special properties. It is shown that some theoretical arguments point to an equality between the number of particles in the observable universe and the number of particles in the largest self-gravitating photon mean free path sphere (MxPhMFPS.) This equality, supported by observational data, leads to a series of equations that relate in simple manner characteristics of the observable universe with characteristics of the MxPhMFPS, and allows a more precise approximation of the values of the main cosmological parameters. It is also shown that by replacing the protons in the MxPhMFPS with positrons, the radiation resulted by their interaction with the existing electrons has an energy equal to the energy of the electromagnetic radiation in the observable universe.     

On the ionization of interstellar magnesium

It has been shown that two concentric ionization zones of interstellar magnesium must exist around each star: internal, with a radius coinciding with that of the zone of hydrogen ionizationS _H; and external, with a radius greater thanS _H, by one order. Unlike interstellar hydrogen, interstellar magnesium is ionized throughout the Galaxy. It also transpires that the ionizing radiation of ordinary hot stars cannot provide for the observed high degree of ionization of interstellar magnesium. The discrepance can be eliminated by assuming the existence of circumstellar clouds or additional ionization sources of interstellar magnesium (X-ray background radiation, high-energy particles, etc.). Stars of the B5 and B0 class play the main role in the formation of ionization zones of interstellar magnesium; the contribution of O class stars is negligible (<1%).     

Modeling the emission processes in blazars

Blazars are the most violent steady/recurrent sources of high-energy gamma-ray emission in the known Universe. They are prominent emitters of electromagnetic radiation throughout the entire electromagnetic spectrum. The observable radiation most likely originates in a relativistic jet oriented at a small angle with respect to the line of sight. This review starts out with a general overview of the phenomenology of blazars, including results from a recent multiwavelength observing campaign on 3C279. Subsequently, issues of modeling broadband spectra will be discussed. Spectral information alone is not sufficient to distinguish between competing models and to constrain essential parameters, in particular related to the primary particle acceleration and radiation mechanisms in the jet. Short-term spectral variability information may help to break such model degeneracies, which will require snap-shot spectral information on intraday time scales, which may soon be achievable for many blazars even in the gamma-ray regime with the upcoming GLAST mission and current advances in Atmospheric Cherenkov Telescope technology. In addition to pure leptonic and hadronic models of gamma-ray emission from blazars, leptonic/hadronic hybrid models are reviewed, and the recently developed hadronic synchrotron mirror model for TeV γ-ray flares which are not accompanied by simultaneous X-ray flares (“orphan TeV flares”) is revisited. The U.S. Government’s right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.