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F. V. Prigara

Publications and source records attributed to F. V. Prigara.

17 recordsLinked to original sources
arXiv2004

Induced radio and X-ray emission from an accretion disk

Radio and X-ray emission from compact sources with accretion disks (active galactic nuclei, pulsars and X-ray binaries) is considered. It is shown that both radio and X-ray emission from these sources can be interpreted as emission of a hot ($T \geqslant 3 \times 10^{7}K$) plasma in the inner part of an accretion disk or in the disk corona. Radio emission is produced by the maser amplification of thermal radio emission in a hot plasma and corresponds to the transitions between highly located energy levels (somewhat similarly to the recombination lines). The X-ray emission is either thermal radiation from dense filaments or is produced by the coherent inverse Compton scattering of radio photons in the same dense filaments. The same mechanism, which gives rise to the maser amplification at radio wavelengths, produces also laser amplification in optical in X-ray binaries.

astro-ph↗
arXiv2004

Effect of stimulated radiation processes on formation of tracks and nanocavities in solids

It is shown that the average diameter of tracks produced by swift heavy ions in metals is determined by the size of elementary resonator. The last is introduced in the theory of thermal radiation accounting for the stimulated radiation processes. Due to the inverse density gradient, radiation produced by electronic excitations is locked in the region of track which is formed. Similar effects are applied to the process of nanocavity formation in semiconductors during ion irradiation.

cond-mat.mtrl-sci↗
arXiv2004

Radiation-induced solitary waves in hot plasmas

It is argued that, in a hot plasma interacting with thermal radiation, there exist the radiation-induced solitary waves different from the types of nonlinear waves in plasmas known so far. There are extensive observational evidence for the propagation of these specific density waves in the hot plasmas of various astrophysical objects. Radiation produces also non-adiabatic density perturbations analogues to the second sound in the liquid helium.

physics.plasm-ph↗
arXiv2004

Thermal radiation from an accretion disk

An effect of stimulated radiation processes on thermal radiation from an accretion disk is considered. The radial density waves triggering flare emission and producing quasi-periodic oscillations in radiation from an accretion disk are discussed. It is argued that the observational data suggest the existence of the weak laser sources in a two-temperature plasma of an accretion disk.

astro-ph↗
arXiv2004

An effect of stimulated radiation processes on radio emission from major planets

The standard theory of thermal radio emission encounters some difficulties. The most crucial one is nonpossibility to explain the radio spectrum of Venus in the decimeter range (Ksanfomality 1985). The radio spectra of planetary nebulae at high frequencies also are not comfortably consistent with the standard theory (Siodmiak & Tylenda 2001). Here we show that the account for an induced character of radiation processes sufficiently improves the predictions of the standard theory.

astro-ph↗
arXiv2003

The energy distribution of atoms in the field of thermal radiation

Using the principle of detailed balance and the assumption on the absorption cross-section consistent with available astrophysical data, we obtain the energy distribution of atoms in the field of thermal blackbody radiation and show that this distribution diverges from the Boltzmann law. There is an inversion of the high energy level population at sufficiently high temperatures.

astro-ph↗
arXiv2003

The wavelength dependence of polarization in active galactic nuclei

Using the gaseous disk model and the condition for emission based on a stimulated origin of thermal radio emission (Prigara 2003), we received the wavelength dependence of polarization for radio emission from active galactic nuclei consistent with available observational data. The strength of magnetic field required to produce an observable degree of polarization in active galactic nuclei is discussed.

astro-ph↗
arXiv2003

An accretion disk and radio spectra of pulsars

On the basis of the unified model of compact radio sources, the dependence of a turnover frequency in the smoothed radio spectrum of a pulsar upon the ratio of the dispersion measure to the period of a pulsar is obtained. This relation is produced by the radial density wave in the accretion disk surrounding a pulsar. The unified model of compact radio sources gives also the smoothed spectral indices of radio emission from pulsars as $α=2$ for the gaseous disk with the temperature profile T=const and $α=3$ for the gaseous disk with the pressure profile P=const ($F_ν \propto ν^{- α} $).

astro-ph↗
arXiv2003

An effect of stimulated radiation processes on radio emission from extended sources

Both the standard theory of thermal radio emission and the synchrotron theory encounter some difficulties. The most crucial for the former one is nonpossibility to explain the radio spectrum of Venus in the decimeter range (Ksanfomality 1985). The radio spectra of planetary nebulae at high frequencies also are not comfortably consistent with the standard theory (Siodmiak & Tylenda 2001). Here we show that the account for an induced character of radiation processes sufficiently improves the predictions of the standard theory. Moreover, the developed here theory of radio emission from non-uniform gas gives the radio spectra of extended sources, such as supernova remnants and radio galaxies, which are normally attributed to the synchrotron emission. It is important, in this aspect, that the synchrotron self-absorption produces a change in the polarization position angle across the spectral peak. No such a change was detected in gigahertz-peaked spectrum sources (Mutoh et al. 2002). Besides, the flat or slightly inverted radio spectra of low-luminosity active galactic nuclei are not easily consistent with the synchrotron radiation mechanism (Nagar, Wilson & Falcke 2001, Ulvestad & Ho 2001). Thermal radiation in a magnetic field is polarized (see, e.g., Lang 1978). This is also true for radiation considered in the present paper, which can be described as incoherent induced radiation (Prigara 2001b).

astro-ph↗
arXiv2002

Einstein's coefficients and the nature of thermal blackbody radiation

We show that thermal radio emission has an induced character and argue that thermal blackbody radiation in other spectral ranges also has an induced origin. A new theory of thermal radio emission of non-uniform gas basing on the induced origin of emission and its astrophysical applications are considered. The nature of emission from various astrophysical objects is discussed.

astro-ph↗
arXiv2002

The wavelength dependence of Sgr A* size and the unified model of compact radio sources

Using, in particular, the data upon Sgr A*, we propose the unified model of compact radio sources, i.e. of pulsars, maser sources, and active galactic nuclei. The unification is based on the wavelength dependence of radio source size. It is shown that the compact sources are characterized by a maser amplification of thermal radio emission. The density, temperature, and magnetic field profiles of compact sources are discussed. The wavelength dependence of Sgr A* size is explained by the effect of the gravitational field of a central energy source on a gas flow.

astro-ph↗
arXiv2002

The density profile and the wavelength dependence of compact radio source size

In the gaseous disk model, the density profile is derived from the mass and energy conservation in the gravitational field of a central energy source. Using the condition for emission, following from the induced character of radiation process, we obtain the wavelength dependence of radio source size which is consistent with observational data.

astro-ph↗
arXiv2002

The unified model of compact radio sources

We propose the unified model of compact radio sources, i.e. of pulsars, maser sources, and active galactic nuclei. The unification is based on the wavelength dependence of radio source size. It is shown that the compact sources are characterized by a maser amplification of thermal radio emission. The density, temperature, and magnetic field profiles of compact sources are discussed.

astro-ph↗
arXiv2002

The Nature of Thermal Blackbody Radiation

It was shown recently that thermal radio emission has a stimulated character, and it is quite possible that thermal black body radiation in other spectral ranges also has an induced origin. The induced origin of thermal black body emission leads to important astrophysical consequences, such as the existence of laser type sources and thermal harmonics in stellar spectra.

astro-ph↗
arXiv2001

Einstein's coefficients and the nature of thermal radio emission

The relations between Einstein's coefficients for spontaneous and induced emission of radiation with account for the natural linewidth are obtained . It is shown that thermal radio emission is stimulated one . Thermal radio emission of non-uniform gas is considered .

astro-ph↗