Search NASA⌕ Search

SEARCH · Search NASA

Results for “relativistic electrons”

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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Ion trajectories in a space-charge wave on a relativistic electron beam

The motion of an ion in a space-charge wave on a strongly magnetized electron beam is investigated. The motions of the ion perpendicular and parallel to the beam direction are coupled by a nonlinear term in the ion Hamiltonian that is proportional to the wave amplitude, and this coupling causes the motion of the ion to deviate significantly from that of a linear harmonic oscillator in certain resonant regions of phase space. A sequence of canonical transformations is employed to investigate the motion of the ion in these regions. It is determined that wave amplitudes that are too small to trap beam electrons are too small to cause these resonances to overlap. When this overlap does not occur, the motion is found not to be discernibly ergodic in any three-dimensional subspace of the energy hypersurface because there exists a third constant of the motion in addition to the total energy and angular momentum. The numerically integrated ion trajectories are studied using surface-of-section techniques in order to verify these findings. It is found that the third constant of the motion constrains an ion initially trapped in a potential well of the wave to remain trapped in this well. It is concluded that ergodic behavior poses no threat at attempts at collective ion acceleration in space-charge waves on an electron beam.

Russell, D. A.↗
NASA NTRS1984

Solar He-3-rich events and non-relativistic electron events: A new association

In 15 months of observation by the ISEE-e spacecraft, it was found that virtually all solar greater than or approximately equal to 1.3 MeV/nucleon He-3-rich events are associated with impulsive 2 to approximately 100 keV electron events, although many electron events were not accompanied by detectable He-3 increases. Both the He-3 and the electrons exhibit nearly scatter-free propagation in the interplanetary medium, and the times of onset and maximum for the He-3 and electron increases are closely related by velocity dispertion. The electron events and their related type III solar radio bursts provide, for the first time, identification of the flares which produce He-3-rich events. He-3 appears to be accelerated at the flash phase of solar flares along with nonrelativistic electrons.

Reames, D. V.↗
NASA NTRS1985

The 3HE in solar non-relativistic electron events

The presence of 3He in 187 solar electron events observed on the ISEE-3 spacecraft during a 9-month period beginning in Aug. 1978 is reported. The 3He is present in over half of the events and in 2/3 of events with 19 keV electrons. It is suggested that 3He would be found in all electron events if these was a greater collection efficiency.

Reames, D. V.↗
NASA NTRS1986

Amplification of electromagnetic waves by a ring-beam distribution of moderately relativistic electrons

The possibility of a new mechanism for the excitation of unstable modes in cold background plasmas is indicated in this paper. These beam-cyclotron modes are excited by the presence of the ring-beam distribution of suprathermal electrons. The usual eigenmode excitation of a cold plasma is reviewed, and the new type of instability is examined using a single-harmonic approximation and multiharmonic treatment.

Shi, B. R.↗
NASA NTRS1987

Analytic and numerical calculations of quantum synchrotron spectra from relativistic electron distributions

Calculations are performed numerically and analytically of synchrotron spectra for thermal and power-law electron distributions using the single-particle synchrotron power spectrum derived from quantum electrodynamics. It is found that the photon energy at which quantum effects appear is proportional to temperature and independent of field strength for thermal spectra; quantum effects introduce an exponential roll-off away from the classical spectra. For power law spectra, the photon energy at which quantum effects appear is inversely proportional to the magnetic field strength; quantum effects produce a steeper power law than is found classically. The results are compared with spectra derived from the classical power spectrum with an energy cutoff ensuring conservation of energy. It is found that an energy cutoff is generally an inadequate approximation of quantum effects for low photon energies and for thermal spectra, but gives reasonable results for high-energy emission from power-law electron distributions.

Brainerd, J. J.↗
NASA NTRS1987

Ion and relativistic electron acceleration by Alfven and whistler turbulence in solar flares

A model is proposed in which turbulent Alfven and whistler waves simultaneously produce the proton and electron spectra implied by the gamma-ray observations noted during the impulsive phase of the June 3, 1982 flare. The results demonstrate that protons can be accelerated to several GeV in less than about 10 sec by Alfven turbulence whose energy density is greater than a few erg/cu cm. It is also found that electrons may be accelerated to tens of MeV on similar time scales by whistler and Alfven turbulence. A lower limit on the energy density of the Alfven turbulence is obtained which is small compared to the total magnetic energy density.

Miller, James A.↗
NASA NTRS1989

Relativistic electrons in Saturn's inner magnetosphere and an estimate of their synchrotron emission

Energetic electron data obtained by Pioneer 11 during its traversal of Saturn's inner magnetosphere were used as the basis for a quantitative model, for which approximate calculations were made of the absolute intensity and spectral distribution of synchrotron emissions. The results are compared with existing knowledge of synchrotron emissions from the inner magnetosphere of Jupiter. The enormous differences between the synchrotron emissions of the inner magnetospheres of Saturn and Jupiter are discussed.

Van Allen, J. A.↗
NASA NTRS1989

Relativistic electron transport and bremsstrahlung production in solar flares

A Monte Carlo simulation of ultrarelativistic electron transport in solar flare magnetic loops has been developed. It includes Coulomb, synchrotron, and bremsstrahlung energy losses; pitch-angle scattering by Alfven and whistler turbulence in the coronal region of the loop; and magnetic mirroring in the converging magnetic flux tubes beneath the transition region. Depth distributions, time profiles, energy spectra, and angular distributions of the resulting bremsstrahlung emission are calculated. It is found that both the preferential detection of solar flares with greater than 10 MeV emission near the limb of the sun and the observation of ultrarelativistic electron bremsstrahlung from flares on the disk are consequences of the loop transport model. The declining portions of the observed time profiles of greater than 10 MeV emission from solar flares can also be accounted for, and it is proposed that these portions are determined by transport and not acceleration.

Miller, James A.↗
NASA NTRS1992

Stratospheric evidence of relativistic electron precipitation

The hypothesis of Thorne (1977, 1980) and Baker et al. (1986, 1987) that the precipitation of energetic electrons is modifying the high-latitude ozone distribution in the Southern Hemisphere is tested by comparing electron density data from a ground-based partial reflection sounder with simultaneous satellite data on ozone mixing ratios taken at the 40 to 50 km altitude. The results do not support the theory that large electron densities coincide with ozone destruction. There is no evidence, for instance, that the January 15, 1984 ionization event had an associated ozone loss. Further experiments for investigating the relationship between the precipitating electrons and ozone depletion are suggested.

Aikin, Arthur C.↗
NASA NTRS1994

Radial diffusion of relativistic electrons in Neptune's magnetosphere

Measurements of greater than or = 1 MeV electrons in Neptune's magnetosphere from L approximately = 4 to 14 are well represented by solutions of a model radial diffusion equation that includes losses due to absorption by the satellite Proteus. The model provides estimates of the radial diffusion coefficient, which is 5 x 10(exp -8) (L/5)(exp 8)/s, and the outer boundary energy spectrum, which is an exponential with an e-folding energy of 0.1 MeV. The diffusion coefficient is consistent with theoretical estimates based on the assumption that diffusion is driven by atmospheric neutral winds.

Selesnick, R. S.↗
NASA NTRS1996

Mesospheric response to impacting relativistic electrons

Daily maps of the spatial distributions of precipitating energetic electrons were produced for the period 10-20 May 1992. These data will serve as the input for potential changes in upper atmosphere composition.

Chenette, D. L.↗
NASA NTRS1996

Mesospheric Response to Impacting Relativistic Electrons

Daily maps of the spatial distributions of precipitating energetic electrons were produced for the period 10-20 May 1992. These data will serve as the input for potential changes in upper atmosphere composition.

Chenette, D. L.↗
NASA NTRS2006

Dynamic Theory of Relativistic Electrons Stochastic Heating by Whistler Mode Waves with Application to the Earth Magnetosphere

In the Hamiltonian approach an electron motion in a coherent packet of the whistler mode waves propagating along the direction of an ambient magnetic field is studied. The physical processes by which these particles are accelerated to high energy are established. Equations governing a particle motion by group symmetries of the problem were transformed in to a closed pair of nonlinear difference equations. The solutions of these equations have shown there exists the energetic threshold below that the electron motion is regular, and when the initial energy is above the threshold an electron moves stochastically. It is proved that the upper boundary of particle stochastic heating is conditioned by intrinsic property of the particle chaotic motion. Particle energy spectra and pitch angle electron scattering are described by the Fokker-Planck-Kolmogorov equations. It is shown that significant pitch angle diffusion occurs for the Earth radiation belt electrons with energies from a few keV up to a few MeV.

Khazanov, G. V.↗
NASA NTRS2007

Dynamic Theory of Relativistic Electrons Stochastic Heating by Whistler Mode Waves with Application to the Earth Magnetosphere

In the Hamiltonian approach an electron motion in a coherent packet of the whistler mode waves propagating along the direction of an ambient magnetic field is studied. The physical processes by which these particles are accelerated to high energy are established. Equations governing a particle motion were transformed in to a closed pair of nonlinear difference equations. The solutions of these equations have shown there exists the energetic threshold below that the electron motion is regular, and when the initial energy is above the threshold an electron moves stochastically. Particle energy spectra and pitch angle electron scattering are described by the Fokker-Planck-Kolmogorov equations. Calculating the stochastic diffusion of electrons due to a spectrum of whistler modes is presented. The parametric dependence of the diffusion coefficients on the plasma particle density, magnitude of wave field, and the strength of magnetic field is studies. It is shown that significant pitch angle diffusion occurs for the Earth radiation belt electrons with energies from a few keV up to a few MeV.

Khazanov, G. V.↗