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Results for “cyclotron radiation”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1973

The effect of a metallic reflector upon cyclotron radiation.

A careful study of the effect of a metallic reflector upon cyclotron radiation emanating from a uniform plasma is made in which the angular polarization and frequency dependence of both the cyclotron radiation and the metallic reflector is taken into account. The properties of the metallic reflector then enter in a natural way and share equal status with the properties of the plasma. The radiation coefficient, the ratio of the cyclotron radiation absorbed by the reflector to that generated by the plasma, becomes a function of the electron temperature and the plasma depth to cyclotron radiation (or simply plasma depth). The radiation coefficient is determined for both slab and cylindrical geometries for electron temperatures from 20 to 120 keV and plasma depths from 10 to the 19th to 10 to the 27th MKS. A simple analytic approximation is given for the radiation coefficient for each geometry, and the results are then applied to a low-beta thermonuclear device based on the D-D reaction. For beta of the order of 1 to 2%, and for devices of moderate size, the metallic reflector is incapable of reducing the cyclotron radiation loss below that required for a self-sustained D-D reaction.

Krajcik, R. A.↗
NASA NTRS1971

Cyclotron radiation in hot magnetoplasmas.

The effects of thermal motions on the cyclotron radiation from test particles gyrating in a homogeneous magnetoplasma are studied. These effects take care of all singularities that exist in the theory of cyclotron radiation in cold magnetoplasma - e.g., the divergence in energy loss for small particle energies. Around the hybrid frequencies thermal corrections become of dominant importance. At these frequencies cold-plasma theory breaks down. Thermal effects arise in two ways: by modifying the wave modes known from cold plasma theory, and by the introduction of a new longitudinal wave mode, known as the Bernstein mode. All wave modes are damped (in stable plasmas).

Trulsen, J.↗
NASA NTRS1978

Theory of the accretion column and cyclotron radiation in X ray pulsars

The energetics of the decelerating matter in the accretion column of X-ray pulsars is considered, in particular the Coulomb process. A two zone model is presented to account for the continuum and cyclotron line emission, incorporating a fan-beam radiation scheme, which appears able to explain the observed properties.

Meszaros, P.↗
NASA NTRS1986

Cyclotron maser radiation from a source structure localized perpendicular to the ambient magnetic field

Particle simulations were used to investigate the properties of electromagnetic radiation produced by the cyclotron maser instability in a source region which is localized in the direction perpendicular to the uniform magnetic field. In the procedure used, the simulation model of Pritchett and Strangeway (1985) for the generation of auroral kilometric radiation (AKR) along an auroral field line was modified to include inhomogeneities perpendicular to the magnetic field. The results are compared with the previous homogeneous simulations with regard to efficiency and saturation mechanism and with expectations based on the feedback model. The implications for the generation and propagation of AKR are discussed.

Pritchett, P. L.↗
NASA NTRS1982

Terrestrial kilometric radiation - The cyclotron theory

It is shown that electrons in inverted V events can cause direct, amplified cyclotron emission (x-mode radiation) above the cutoff frequency, and the growth rate of the waves is calculated by using inverted V electron event observations as the inputs of a numerical code. Calculation results exhibiting wave growth are adduced as evidence for the cyclotron interpretation of terrestrial kilometric radiation (TKR). It is speculated that the specific electron distribution features which generate TKR should disappear in much less than a second, and should therefore not be observable in particle data averaged over more than one second. The basic electron distribution feature that gives rise to TKR is a one-sided loss cone anisotropy in which upward moving electrons with small pitch angles are missing. The features causing large growth rates may be due to the effects of the parallel electric field.

Melrose, D. B.↗
NASA NTRS1986

A search for cyclotron maser radiation from substellar and planet-like companions of nearby stars

Several stars within 5 pc have variations in their rectilinear or Keplerian motion that suggest that they have substellar or planetlike companions. However, direct, unambiguous evidence of such companions is difficult to obtain. It is argued that such objects should commonly emit cyclotron maser radiation and that this radiation should be observable with modern radio telescopes. Its detection would confirm the presence of the companions and permit many of the properties of the stars and companions to be derived. A search was made for the cyclotron maser emission from six nearby stars with suspected companions using the VLA at frequencies of 0.33 and 1.4 GHz. None was detected. Typical observing times were 3.5 hr, and typical upper limits were 30 mJy at 0.33 GHz and 0.3 mJy at 1.4 GHz.

Winglee, Robert M.↗
NASA NTRS1991

Kinetic friction attributed to enhanced radiation by cyclotron maser instability

Along the auroral field lines, a fraction of the energetic electrons injected from the magnetotail is reflected by the earth's convergent geomagnetic field. The reflected loss-cone electrons are unstable with respect to the cyclotron maser instability, resulting in the auroral kilometric radiation. This paper investigates the kinetic friction force exerted on the energetic electrons by the enhanced radiation field. It is found that the enhanced radiation results in a deceleration of reflected electrons, thereby providing an effective resistivity. In addition, the rate of decrease (increase) of effective perpendicular (parallel) kinetic temperatures is also evaluated. The analysis is carried out over various physical parameters such as the degree of loss cone, average particle energy, and the ratio of plasma frequency to cyclotron frequency.

Yoon, Peter H.↗
NASA NTRS1984

Electron-cyclotron maser radiation from a relativistic loss-cone distribution

A relativistic analysis of the electron-cyclotron maser instability in a loss-cone distribution is presented, extending the treatment of Lau and Chu (1983) to include the effects of finite k-perpendicular (as encountered in laboratory tandem-mirror devices with mean energies in excess of 50 keV). The results are presented in graphs, and it is found that the k-perpendicular effects are significant, so that emission perpendicular to the magnetic field is associated with most rapid growth of the instability. The persistence of the instability when the ratio of the plasma frequency to the electron-cyclotron frequency is less than 0.1 is demonstrated, and the factors which need to be accounted for in applying the results to actual mirror devices are indicated.

Pritchett, P. L.↗
NASA NTRS1988

Circular polarimetry of EXO 033319-2554.2 - A new eclipsing AM Herculis star

This Letter presents circular polarimetry that unequivocally identifies EXO 033319-2554.2 as only the third eclipsing AM Her star and brings the total number of AM Her stars now identified to 14. The orbital period is 126.4 minutes, as previously reported, and defines a new short-period edge to the period gap seen in all classes of cataclysmic variable stars. EXO 033319-2554.2 shows 2.5 mag deep eclipses of the predominantly accreting magnetic pole on the white dwarf. Before the eclipse, the pole rotates into the line of sight and shows white-light circular polarization, due to cyclotron radiation, that reaches values as high as 10 percent. There is some evidence that the second pole is emitting cyclotron radiation too. How high time resolution photometry, linear polarimetry, and spectroscopy will be of great value in understanding this system.

Berriman, Graham↗
NASA NTRS1980

Amplification of radiation near cyclotron frequency due to electron population inversion

Amplification of electromagnetic waves via the cyclotron maser mechanism by a population of weakly relativistic electrons is studied. The effect of a tenuous population of low energy background plasma is included. It is found that both the ordinary and extraordinary modes can be excited by the weakly relativistic electrons with a loss-cone distribution. The growth rate for the extraordinary mode is much higher than that for the ordinary mode. Velocity spread in the energetic electron distribution function may reduce the growth rate by a factor of approximately 10 from that in the monoenergetic case. The maximum growth rate for the fast extraordinary mode (X mode) occurs near the upper hybrid cutoff frequency. Numerical results are obtained and discussed.

Lee, L. C.↗
NASA NTRS1989

Propagation and absorption of electron-cyclotron maser radiation during solar flares

The propagation and absorption of the maser radiation during solar flares are examined through linear theory and electromagnetic particle simulations. It is shown using linear theory that strong absorption of the radiation should occur as it propagates toward the second harmonic layer, where the magnetic field is half as strong as in the emission region. Only radiation propagating nearly parallel to the magnetic field in a low-temperature plasma may be able to escape under certain limited conditions. Finite temperature effects can cause radiation propagating nearly perpendicular to the magnetic field to refract, causing enhanced absorption. Particle simulations are then used to evaluate the nonlinear response of the plasma as the maser radiation propagates through the absorption layer. It is shown that some of the maser radiation is able to escape through a process of absorption below the second harmonic of the local gyrofrequency and re-emission above it. The fraction able to escape is much higher than that predicted by linear theory, although the amount of escaping energy is only a small fraction of the incident energy.

Mckean, M. E.↗
NASA NTRS1980

Cosmic gamma-ray lines - Theory

The various processes that lead to gamma-ray line emission and the possible astrophysical sources of such emission are reviewed. The processes of nuclear excitation, radiative capture, positron annihilation, and cyclotron radiation, which may produce gamma-ray line emission from such diverse sources as the interstellar medium, novas, supernovas, pulsars, accreting compact objects, the galactic nucleus and the nuclei of active galaxies are considered. The significance of the relative intensities, widths, and frequency shifts of the lines are also discussed. Particular emphasis is placed on understanding those gamma-ray lines that have already been observed from astrophysical sources.

Lingenfelter, R. E.↗
NASA NTRS1978

Gamma-ray lines - A new window to the Universe

Gamma-ray emission is considered in terms of its usefulness in determining the physics of nucleosynthesis, the interstellar medium, solar flares, supernovae, and neutron stars. The mechanism of gamma-ray line emission is reviewed, i.e., nuclear deexcitation, radiative capture, positron annihilation, and possibly cyclotron radiation in the strong magnetic fields of neutron stars. Various gamma-ray spectra, obtained from balloon and satellite data, are analyzed with attention to solar particle energies and densities, including particle emission from black-hole supernova remnants.

Lingenfelter, R. E.↗