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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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At least 199 records · Page 11
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NASA NTRS1973

Amplitude variations of whistler-mode signals caused by their interaction with energetic electrons of the magnetosphere

Whistler mode waves that propagate through the magnetosphere exchange energy with energetic electrons by wave-particle interaction mechanisms. Using linear theory, a detailed investigation is presented of the resulting amplitude variations of the wave as it propagates. Arbitrary wave frequency and direction of propagation are considered. A general class of electron distributions that are nonseparable in particle energy and pitch-angle is proposed. It is found that the proposed distribution model is consistent with available whistler and particle observations. This model yields insignificant amplitude variation over a large frequency band, a feature commonly observed in whistler data. This feature implies a certain equilibrium between waves and particles in the magnetosphere over a wide spread of particle energy, and is relevant to plasma injection experiments and to monitoring the distribution of energetic electrons in the magnetosphere.

Bernard, L. C.↗
NASA NTRS1973

ATS-5 observations of energetic proton injection

Energetic particle observations from ATS-5 are presented that directly show asymmetric injection of 30- to 300-keV proton fluxes into the nightside magnetosphere to form the asymmetric ring current. The temporal structure of these substorm-correlated proton bursts is consistent with a westward gradient drift from the nightside acceleration region. The drifting protons tend to be accompanied by nondiamagnetic decreases of the magnetic field at the satellite. Adiabatic decreases of the energetic electron fluxes often occur with these changes in the field strength. Nearly 200 proton-only events have been observed, occurring uniformly between 1500 and 2200 LT and not at all before 1200 LT or after 2300 LT.

Bogott, F. H.↗
NASA NTRS1973

Cyclotron resonance wave amplification in the magnetosphere and energetic particle stability

Detailed electron distribution measurements in the outer magnetosphere now available indicate that the energetic electron anisotropy may be very energy dependent, there being positive anisotropies near the magnetic equator for low-energy particles and negative anisotropies in this region for high-energy particles. Previous wave growth calculations assuming the energetic particle anisotropy to be independent of energy are inaccurate at high energies. The net one-hop whistler mode wave amplification is calculated as a function of frequency for a measured electron distribution at L = 7 for a number of assumed equatorial plasma densities. It is found that an increase in cold plasma density results in a change from a net wave damping to significant wave amplification.

Lucas, C.↗
NASA NTRS1974

Energetic electrons in Jupiter's magnetosphere

A theoretical model for the energetic electron fluxes in the Jovian magnetosphere is developed. Electrons are transported inward from the solar wind or Jovian magnetospheric tail by radial diffusion. The radial diffusion is driven by fluctuating ionospheric dynamo electric fields associated with a neutral-wind tidal eigenmode at ionospheric altitudes. The tidal mode is excited by the electromagnetic coupling of the solar wind to the polar ionosphere. Two injection models are considered: (1) electron penetration through the dayside magnetopause - low-energy model; and (2) injection of electrons from an assumed magnetospheric tail - high-energy model. Both thermal solar-wind electrons and energetic solar-flare electrons are considered.

Coroniti, F. V.↗
NASA NTRS1975

Plasma wave interactions with energetic ions near the magnetic equator

An intense band of electromagnetic noise is frequently observed near the magnetic equatorial plane at radial distance from about 2 to 5 Re. Recent wideband wave-form measurements with the IMP-6 and Hawkeye-1 satellites have shown that the equatorial noise consists of a complex superposition of many harmonically spaced lines. Several distinctly different frequency spacings are often evident in the same spectrum. The frequency spacing typically ranges from a few Hz to a few tens of Hz. It is suggested that these waves are interacting with energetic protons, alpha particles, and other heavy ions trapped near the magnetic equator. The possible role these waves play in controlling the distribution of the energetic ions is considered.

Gurnett, D. A.↗
NASA NTRS1975

Recirculation of energetic particles in Jupiter's magnetosphere

A significant new finding from analysis of Pioneer 11 observations in the magnetosphere of Jupiter is that there is net streaming of both electrons E above 40 keV and E above 560 keV and protons in the range from .61 to 3.41 MeV away from the planet along high-latitude field lines. This result is compatible with the recent suggestion of Nishida that energetic particles undergo trans-L shell diffusion at low altitudes without significant change of energy. This provides a plausible explanation for the remarkable pitch angle distributions near the equator in the range of L values from 12 to 25; the presence of particles of about 1 MeV energy at the outer edge of the magnetosphere; and hence, via conventional inward diffusion processes, the presence of those having magnetic moments of several hundred MeV per gauss in the inner magnetosphere. The recirculation of energetic particles emerges as an important dynamical feature of the Jovian magnetosphere.-

Sentman, D. D.↗
NASA NTRS1976

Plasma wave interactions with energetic ions near the magnetic equator

An intense band of electromagnetic noise is frequently observed near the magnetic equatorial plane at radial distance from about 2 to 9 earth radii. Recent wide band wave form measurements with the Imp 6 and Hawkeye 1 satellites have shown that the equatorial noise consists of a complex superposition of many harmonically spaced lines. Several distinctly different frequency spacings are often evident in the same spectrum. The frequency spacing typically ranges from a few hertz to a few tens of hertz. The purpose of this paper is to suggest that these waves are interacting with energetic protons, alpha particles, and other heavy ions trapped near the magnetic equator. The possible role that these waves play in controlling the distribution of the energetic ions is considered.

Gurnett, D. A.↗
NASA NTRS1977

Observations of energetic electrons /E no less than about 200 keV/ in the earth's magnetotail - Plasma sheet and fireball observations

An earlier paper by the authors (1976) has reported on energetic electron anisotropies observed in conjunction with the acceleration regions identified by Frank et al., (1976). The present paper gives more detailed analyses of observations in the distant plasma sheet, including specific features of intensities, energy spectra, and pitch angle distributions of the very energetic electrons associated with intense plasma particle events, with energies ranging between 50 eV and 45 keV, detected with an electron/isotope spectrometer aboard the earth-orbiting spacecraft Imp 8. Two domains are considered: the plasma sheet and the regions near and within the localized magnetotail acceleration regions known as the fireball regions. The instrumentation used offered a number of observational advantages over many previous studies, including inherently low background, large geometric factors, excellent species identification, good angular distribution measurement capability, and availability of high resolution of differential intensities.

Baker, D. N.↗
NASA NTRS1978

The composition of corotating energetic particle streams

The relative abundances of 1.5 to 23 MeV/nucleon ions in corotating nucleon streams were compared with ion abundances in particle events associated with solar flares and with solar and solar wind abundances. He/O and C/O ratios were found to be a factor of the order two to three times greater in corotating streams than in flare associated events. The distribution of H/He ratios in corotating streams was found to be much narrower and of lower average value than in flare associated events. H/He in corotating energetic particle streams compared favorably both in lack of variability and numerical value to H/He in high speed solar wind plasma streams. This comparison suggested that the source population for the corotating energetic particles was the solar wind.

Mcguire, R. E.↗
NASA NTRS1977

Evaluation of energetic particle effects on BUV data and atmospheric ozone

To aid investigations of energetic particle effects on the backscattered ultraviolet (BUV) instrumentation aboard Nimbus 4, solar proton events characterized as polar cap absorption events occurring in the period April 1970 to April 1976 were summarized. Energetic particle effects on total ozone above the 4 mb pressure level measured by Nimbus 4 were analyzed. Proceedings of a workshop meeting of operation aurorozone are included as background material for possible effects of bremsstrahlung on atmospheric ozone.

Herman, J. R.↗
NASA NTRS1978

Probing the solar corona with energetic particles

Representative sets of recent experimental results and theoretical studies are summarized to show the current knowledge of energetic particle phenomena based mainly on observations near 1 AU. Measurements close to the sun of quantities such as particle spectra, charge and isotopic composition, and the flow of particles as a function of time, together with measurements of the plasma, magnetic field, X-rays, and gamma rays will not only reveal the properties of the source region and acceleration mechanisms but will also provide a better knowledge of the physics of the corona. These measurements may also reveal the existence of large scale inhomogeneities in the solar corona. The general requirements for making these measurements on the solar probe are listed. An energetic particle detector system which has the capability of resolving the charge and isotopic composition up to 50 MeV/nucleon may successfully measure the above quantities provided that it can perform under both very low and average intensity levels.

Vanhollebeke, M. A. I.↗
NASA NTRS1978

Correction to 'Recirculation of energetic particles in Jupiter's magnetosphere'

An error in Pioneer 11 data reduction software has, when present, caused a phase shift of 180 deg in the assignment of spacecraft roll angles. The corrected analysis of the pitch angle distributions of energetic particles in Jupiter's magnetosphere reveals significant proton anisotropies directed toward the planet in the southern hemisphere, contrary to the authors' (1975) original report. In the northern hemisphere, both proton and electron anisotropies are directed away from the planet, as reported previously. The revised data show that the claim of direct evidence for the hypothesis of recirculation of energetic particles in the Jovian magnetosphere is invalid. It is suggested that indirect evidence still supports the hypothesis, although the recirculation process must be weaker than originally envisioned and obscured by other processes.

Sentman, D. D.↗
NASA NTRS1978

The composition of corotating energetic particle streams

The relative abundances of 1.5-23 MeV per nucleon ions in corotating nucleon streams are compared with ion abundances in particle events associated with solar flares and with solar and solar wind abundances. He/O and C/O ratios are found to be a factor of the order 2-3 greater in corotating streams than in flare-associated events. The distribution of H/He ratios in corotating streams is found to be much narrower and of lower average value than in flare-associated events. H/He in corotating energetic particle streams compares favorably in both lack of variability and numerical value with H/He in high-speed solar wind plasma streams. The lack of variability suggests that the source population for the corotating energetic particles is the solar wind, a suggestion consistent with acceleration of the corotating particles in interplanetary space.

Mcguire, R. E.↗
NASA NTRS1978

Simultaneous multispacecraft observations of energetic proton bursts inside and outside the magnetosphere

Energetic proton bursts were observed simultaneously on Imp 6, 7, and 8 both inside and outside the earth's magnetosphere during the period October 1972 through August 1974. It is found that proton bursts are present nearly simultaneously in the vicinity of the outer belt trapping boundary, in the low-latitude magnetotail, in the magnetosheath, and upstream from the bow shock. Large intensity differences, time delays, and differences in energy spectra recorded by the three spacecraft are described. It is suggested that energetic protons and electrons are probably accelerated inside the plasma sheet and propagate to various regions both inside and outside the magnetosphere.

Sarris, E. T.↗
NASA NTRS1978

The magnetopause energetic electron layer. I - Observations along the distant magnetotail

Instrumentation aboard Imp 8 was used to study the magnetopause energetic electron layer along the distant magnetotail, and the observations are discussed. The inner edge of the layer corresponds to the magnetopause boundary, and energetic electrons within the layer persistently stream tailward along local magnetosheath field lines. Pitch angles of electrons along the dusk magnetopause are often restricted to values less than approximately 40 deg, while along the dawnside of the tail somewhat larger pitch angles are normally seen. The differential energy spectra of electrons in the layer, the intensity enhancements, and the average directional intensities are characterized.

Baker, D. N.↗
NASA NTRS1978

Nuclear gamma rays from energetic particle interactions

Gamma ray line emission from nuclear deexcitation following energetic particle reactions is evaluated. The compiled nuclear data and the calculated gamma ray spectra and intensities can be used for the study of astrophysical sites which contain large fluxes of energetic protons and nuclei. A detailed evaluation of gamma ray line production in the interstellar medium is made.

Ramaty, R.↗
NASA NTRS1979

A rocket-borne electrostatic analyzer for measurement of energetic particle flux

A rocket-borne electrostatic analyzer experiment is described. It is used to measure energetic particle flux (0.9 to 14 keV) in the nighttime midlatitude E region. Energetic particle precipitation is believed to be a significant nighttime ionization source, particularly during times of high geomagnetic activity. The experiment was designed for use in the payload of a Nike Apache sounding rocket. The electrostatic analyzer employs two cylindrical parallel plates subtending a central angle of 90 deg. The voltage waveform supplied to the plates is a series of steps synchronized to the spin of the payload during flight. Both positive and negative voltages are provided, extending the detection capabilities of the instrument to both electrons and protons (and positive ions). The development, construction and operation of the instrument is described together with a preliminary evaluation of its performance in a rocket flight.

Pozzi, M. A.↗
NASA NTRS1978

Effects of the solar wind on magnetospheric dynamics: Energetic electrons at the synchronous orbit

A correlation of the observations of energetic electron fluxes at the synchronous orbit with the interplanetary medium and the behavior of energetic trapped radiation at the synchronous altitude were analyzed. Data covering the 1967 to 1978 interval were obtained by the ATS 1, ATS 5, and ATS 6 spacecraft. Long term (year) and short term (days) electron flux averages are found to correlate positively with corresponding averages of the solar wind velocity.

Paulikas, G. A.↗