Search NASA⌕ Search

SEARCH · Search NASA

Results for “relativistic”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Relativistic effects of the rotation of the earth on remote clock synchronization

A treatment is given of relativistic clock synchronization effects due to the rotation of the earth. Unlike other approaches, the point of view of an earth fixed coordinate system is used which offers insight to many problems. An attempt is made to give the reader an intuitive grasp of the subject as well as to provide formulae for his use. Specific applications to global timekeeping, navigation, VLBI, relativistic clock experiments, and satellite clock synchronization are discussed. The question of whether atomic clocks are ideal clocks is also treated.

Reinhardt, V.↗
NASA NTRS1976

Relativistic electrons and whistlers in Jupiter's magnetosphere

The path-integrated gain of parallel propagating whistlers driven unstable by an anisotropic distribution of relativistic electrons in the stable trapping region of Jupiter's inner magnetosphere was computed. The requirement that a gain of 3 e-foldings of power balance the power lost by imperfect reflection along the flux tube sets a stably-trapped flux of electrons which is close to the non-relativistic result. Comparison with measurements shows that observed fluxes are near the stably-trapped limit, which suggests that whistler wave intensities may be high enough to cause significant diffusion of electrons accounting for the observed reduction of phase space densities. A crude estimate of the wave intensity necessary to diffuse electrons on a radial diffusion time scale yields a lower limit for the magnetic field fluctuation intensity.

Barbosa, D. D.↗
NASA NTRS1975

The relativistic equations of stellar structure and evolution

The general relativistic equations of stellar structure and evolution are reformulated in a notation which makes easy contact with Newtonian theory. A general relativistic version of the mixing-length formalism for convection is presented. It is argued that in work on spherical systems, general relativity theorists have identified the wrong quantity as total mass-energy inside radius r.

Thorne, K. S.↗
NASA NTRS1976

The relativistic equations of stellar structure and evolution. Stars with degenerate neutron cores. 1: Structure of equilibrium models

The general relativistic equations of stellar structure and evolution are reformulated in a notation which makes easy contact with Newtonian theory. Also, a general relativistic version of the mixing-length formalism for convection is presented. Finally, it is argued that in previous work on spherical systems general relativity theorists have identified the wrong quantity as "total mass-energy inside radius r."

Thorne, K. S.↗
NASA NTRS1977

The relativistic equations of stellar structure and evolution

The general-relativistic equations of stellar structure and evolution are reformulated in a notation which makes easy contact with Newtonian theory. Also, a general-relativistic version of the mixing-length formalism for convection is presented.

Thorne, K. S.↗
NASA NTRS1977

On the hydrodynamic expansion of a relativistic gas

An exact solution to the one-dimensional relativistic Euler equations is presented which is not of a self-similar nature and which satisfies certain initial conditions found to be appropriate in describing high-energy cosmic-ray collisions and models of radio galaxies. A full numerical analysis is performed to demonstrate the temporal behavior of all relevant thermodynamic quantities at any given point in the expansion. The results indicate that the motion is self-similar at the very beginning of free expansion, that this description ceases to be valid when the entire bulk of fluid is in motion, and that with the passage of time, the nonsimilar solution prevails over more and more of the fluid except for a small region near the leading edge where the fluid borders on the vacuum. The very bulk of the expansion is shown to become nonsimilar because the leading edge of the self-similar solution moves into the vacuum at the speed of light while that of the nonsimilar solution approaches c only asymptotically. The relativistic expansion of a gaseous disk is analyzed as an example.

Canuto, V.↗
NASA NTRS1978

Graphical evaluation of relativistic matrix elements

A graphical representation of angular momentum was used to evaluate relativistic matrix elements between antisymmetrized states of many particle configurations having any number of open shells. The antisymmetrized matrix element was expanded as a sum of semisymmetrized matrix elements. The diagram representing a semisymmetrized matrix element was composed of four diagram blocks; the bra block, the ket block, the spectator block, and the interaction block. The first three blocks indicate the couplings of the two interacting configurations while the last depends on the interaction and is the replaceable component. Interaction blocks for relativistic operators and commonly used potentials were summarized in ready to use forms. A simple step by step procedure was prescribed generally for calculating antisymmetrized matrix elements of one and two particle operators.

Huang, K. N.↗
NASA NTRS1978

General-relativistic astrophysics

The overall relevance of general relativity to astrophysics is considered, and some of the knowledge about the ways in which general relativity should influence astrophysical systems is reviewed. Attention is focused primarily on finite-sized astrophysical systems, such as stars, globular clusters, galactic nuclei, and primordial black holes. Stages in the evolution of such systems and tools for studying the effects of relativistic gravity in these systems are examined. Gravitational-wave astronomy is discussed in detail, with emphasis placed on estimates of the strongest gravitational waves that bathe earth, present obstacles and future prospects for detection of the predicted waves, the theory of small perturbations of relativistic stars and black holes, and the gravitational waves such objects generate. Characteristics of waves produced by black-hole events in general, pregalactic black-hole events, black-hole events in galactic nuclei and quasars, black-hole events in globular clusters, the collapse of normal stars to form black holes or neutron stars, and corequakes in neutron stars are analyzed. The state of the art in gravitational-wave detection and characteristics of various types of detector are described.

Thorne, K. S.↗
NASA NTRS1979

Relativistic electrons in the intracluster space of clusters of galaxies - The hard X-ray spectra and heating of the gas

An appropriate form for the steady-state intracluster relativistic electron energy spectrum is derived, taking into account all the dominant energy loss mechanisms. The Compton X-ray flux is calculated and compared with the soft X-ray thermal flux. The amount of heating of the intracluster gas by energy loss of relativistic electrons in electronic and Alfven wave excitations is estimated.

Rephaeli, Y.↗
NASA NTRS1979

Relativistic L -shell Auger and Coster-Kronig rates and fluorescence yields

Relativistic calculations of radiationless transition rates to L -subshell vacancy states in selected atoms with Z in the 70-96 range have been performed. The Auger and Coster-Kronig transition probabilities are calculated from perturbation theory, assuming frozen orbitals, in the Dirac-Hartree-Slater approach. Transition rates, fluorescence yields, and Coster-Kronig yields are compared with nonrelativistic theoretical results and with experiment. Relativity is found to affect the L -subshell Auger widths by (10-25)% and individual transition rates to certain j-j configurations by as much as 40% at Z = 80. The widths of L sub i vacancy states and the L sub 2 Coster-Kronig yields f33 from these relativistic calculations agree much better with experiment than earlier nonrelativistic theoretical values.

Chen, M. H.↗
NASA NTRS1979

L-shell Auger and Coster-Kronig spectra from relativistic theory

The intensities of L-shell Auger and Coster-Kronig transitions in heavy atoms have been calculated relativistically. A detailed comparison is made with measured Auger spectra of Pt and U. The pertinent transition energies were computed from relativistic wave functions with inclusion of the Breit interaction, self-energy, a vacuum-polarization correction, and complete atomic relaxation. Multiplet splitting is found to distribute Auger electrons from certain transitions among several lines. The analysis leads to reassignment of a number of lines in the measured spectra. Lines originally identified as L2-L3Ni in the U spectrum are shown to arise from M4,5 Auger transitions instead.

Chen, M. H.↗
NASA NTRS1979

Astrophysical gamma-ray production by inverse Compton interactions of relativistic electrons

The inverse Compton scattering of background photon gases by relativistic electrons is a good candidate for the production of high-energy gamma rays in the diffuse interstellar medium as well as in discrete sources. By discussing the special case of the scattering of the diffuse starlight in the interstellar medium by cosmic ray electrons, we demonstrate that previous derivations of the gamma ray source function for this process on the basis of the Thomson limit of the Klein-Nishina cross section lead to incorrect values for gamma-ray energies above 100 MeV. It is shown that the Thomson limit is not applicable for the calculation of gamma-ray source functions in astrophysical circumstances in which target photons with energies greater than 1 eV are scattered by relativistic electrons.

Schlickeiser, R.↗
NASA NTRS1979

Numerical solutions of the trans-relativistic shock relations

Using a slight modification of the Taub adiabat procedure, the paper solves the relativistic Rankine-Hugoniot (RH) relations for transrelativistic shocks in a nondegenerate Fermi gas. A parametric survey of numerical solutions of the RH relations is presented, making it possible to infer by interpolation from graphical displays the solutions to a variety of shocks. In addition, the transrelativistic nature of the solutions is explicit because when the upstream pressure is low, the shocks first approach those given by nonrelativistic strong shock theory and then approach the relativistic strong shock limit as the Mach number increases.

Fujimura, F. S.↗
NASA NTRS1980

Relativistic jets and the continuum emission in QSOs

The radio through optical, and possibly X-ray, emission of QSOs and active galactic nuclei is analytically interpreted in terms of a relativistic jet containing high-energy particles and a magnetic field. Parallel to the jet axis, a strong, compact radio source and strongly polarized radiation are detected, while larger viewing angles relative to the jet axis result in spectral dominance by the central region containing the 'energy machine' which drives the energy flux in the jet. It is shown that the relativistic jet model can explain the association of OVVs with strong, variable radio sources, strong optical polarization, and continuity of the radio to optical spectra.

Marscher, A. P.↗
NASA NTRS1980

Relativistic K-LL Auger spectra in the intermediate-coupling scheme with configuration interaction

Theoretical K-LL Auger spectra from relativistic Dirac-Hartree-Slater calculations in intermediate coupling with configuration interaction (ICWCI) are considered. Calculated transition rates for 25 elements with Z between 18 and 96, inclusive, are listed and compare well with experimental data. Relativistic effects are found to be important above Z equal to about 35, and ICWCI is necessary to describe the spectra for Z less than about 60.

Chen, M. H.↗
NASA NTRS1980

Spontaneous formation of knots in relativistic flows - A model for variability in compact synchrotron sources

A model is proposed in which regions of enhanced synchrotron emission are formed via radiative thermal instabilities in relativistic flows. A perturbed volume in which the magnetic field is enhanced by a few tens of a percent relative to the steady value collapses due to the increased cooling rate and consequent loss in pressure. The collapse further increases the magnetic field, leading to even shorter radiative lifetimes. The instability progresses in this way until either the external electron pressure is balanced by the perturbed magnetic pressure or the overall expansion of the flow becomes important. A fluid-dynamical treatment of the instability is performed, and the results are shown to apply to flux variations and formation of knots in the relativistic flows which are thought to occur in quasars and active galactic nuclei. The knots possess the same kinematic properties as the collimated flow and can thus be responsible for the apparent superluminal motions observed in compact radio sources.

Marscher, A. P.↗
NASA NTRS1980

The heating of gas in clusters of galaxies by relativistic electrons - Collective effects

We show that the rate at which gas is heated in X-ray clusters of galaxies by streaming relativistic electrons can be much greater than the Coulomb heating rate because of the stimulated growth of a high level of electrostatic turbulence and its subsequent collapse to shorter wavelengths. This enhanced heating (and, hence, energy loss) rate allows the X-ray emitting gas to be heated by those particles which are observable through their synchrotron emission at low radio frequencies and yields a radio source size consistent with the observed radio halo sizes in the Coma cluster. The heating of gas in clusters of galaxies by relativistic electrons will significantly affect the cluster gas dynamics.

Scott, J. S.↗
NASA NTRS1980

The effect of convection on the propagation of relativistic galactic electrons

The paper presents exact analytical solutions which describe steady-state transport of relativistic electrons subject to diffusion, convection, and radiation losses. The diffusion coefficient is spatially and energy dependent; the bulk convection velocity is considered to be constant and directed outward from the galactic plane. The electron spectral behavior with respect to galactic height and energy indicates that convection provides a 'break' in the steady-state energy spectrum without recourse to distribution of sources. Radio observations of NGC 891 and NGC 4631 galaxies can be used to estimate their diffusion coefficient and its energy dependence. Application of analytical solutions to our Galaxy indicates that the diffusion coefficient and outflow velocity deduced from relativistic electron measurements and radio observations of their synchrotron radiation agree with values based on the transport of the cosmic ray nucleonic component.

Lerche, I.↗