Search NASA⌕ Search

Engineering topics

Mcdonald, F. B.

Publications and source records attributed to Mcdonald, F. B..

At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Observations of Jovian accelerated particles both inside and outside the Jovian magnetosphere - Results from the Goddard-U. of New Hampshire experiment on Pioneer 10

This paper discusses measurements of the energetic-particle population inside Jupiter's magnetosphere as well as observations of energetic particles in interplanetary space that have escaped from that magnetosphere. The discussion is based on Pioneer 10 data obtained when the spacecraft was outside the bow shock but within about 1 AU of the planet and on electron data obtained near earth by various IMP spacecraft. Pioneer 10 particle measurements in the Jovian magnetosphere are reviewed, the differential proton and electron energy spectra are described, and it is suggested that very little particle acceleration occurs in the outer magnetosphere. Additional data are examined in regard to Jovian alpha particles, proton and electron angular distributions, protons in the inner magnetosphere, effects of Io on the proton flux, electron acceleration outside the bow shock, and observations of Jovian electrons near earth. All these data are shown to support the conclusion that most, if not all, quiet-time increases in low-energy electron fluxes near earth are of Jovian origin.

Trainor, J. H.↗
NASA NTRS1975

IMP 6, 7 and 8 observations of the composition and time variations of low energy cosmic rays

The charge composition and time variations of quiet-time cosmic rays in the energy range 10 to 25 MeV/nucleon were studied to determine the source of the enhancement of quiet-time intensities of low energy nitrogen and oxygen nuclei observed by Pioneer 10. Time variations were established from data from IMPs 6, 7, and 8; the charge composition was obtained by summing data from IMP 7 and IMP 8. The neon to carbon ratio present in solar rays is too low to explain an observed enhancement of neon. Helium and oxygen have the same percentage modulation for a range of x5 in intensity. This can be explained within the framework of the field-force approximation and the selection mechanism based on the first ionization potential proposed by Fisk et al. (1974) if both oxygen and helium are singly charged.

Von Rosenvinge, T. T.↗
NASA NTRS1975

Propagation characteristics of solar flare particles

A statistical study on the propagation characteristics of about 80 solar particle events is carried out using the data from Goddard cosmic-ray experiments. It is found that for particles near onset as well as maximum particle intensity at 1 AU, a linear relation exists between the velocity and the traveled distance. This holds for both relativistic electrons (0.5-1.1 MeV) and nonrelativistic protons (4-80 MeV). The relation indicates that particle propagation is independent of both rigidity and energy. It is shown that in general interplanetary diffusion plays a minor role in particle propagation during the initial phase of a flare effect. A study of the onset characteristics indicates that the speed of particle transport in the corona may be as high as 40 deg/hr. This behavior can not be accounted for by either magnetic-field or curvature drift.

Ma Sung, L. S.↗
NASA NTRS1975

Further studies of the new component of cosmic rays at low energies

Recent observations with cosmic ray telescopes aboard the Pioneer 10 space probe have revealed an anomalous spectrum of nitrogen and oxygen nuclei relative to other nuclei such as carbon in the quiet time cosmic radiation below about 40 MeV/nuc. These observations are extended with additional data from Pioneer 10 and considerable new data from an identical telescope aboard Pioneer 11. In addition to the enhancement of nitrogen and oxygen nuclei observed earlier, the intensity of neon is enhanced as well. The spectra of boron, magnesium, and silicon appear to be similar to that of carbon. Data on the isotopic composition, solar modulation, and radial gradient of these nuclei are presented.

Webber, W. R.↗
NASA NTRS1975

Solar cosmic ray events at large radial distances from the sun

The cosmic ray telescopes on Pioneer 10 and 11 are used to examine solar cosmic ray events out to a distance about 5 AU from the sun. A detailed error analysis of the cosine fit to the anisotropy is presented. The anisotropy and intensity time characteristics during solar events are discussed as a function of radial distance.

Zwickl, R.↗
NASA NTRS1974

Energetic particles in the Jovian magnetosphere

Detail account of the Pioneer 10 encounter with Jupiter as viewed by the Goddard-University of New Hampshire cosmic ray experiment. Flux time histories of electrons and protons are given over a wide energy band. These show a marked variation with magnetic latitude. Significant removal of low-energy protons by Io is apparent in the inner magnetosphere (less than or equal to 6 Jovian radii). Proton and electron energy spectra are given at various Jovicentric distances. The electron spectra are remarkably hard and constant in slope in the 0.12 to 8.0-MeV interval, the electron spectral index having a value of 1.5 to 2.0 in the region outside 25 Jovian radii. Proton spectra are shown to transform from a power law with indices in the 3 to 4.2 range to more nearly exponential forms in the inner regions (less than or equal to 40 Jovian radii). Extensive data are presented on the angular distributions of protons and electrons at various locations in the Jovicentric magnetosphere.

Trainor, J. H.↗
NASA NTRS1974

Interplanetary MeV electrons of Jovian origin

Observation of low-energy (0.2- to 8-MeV) electron increases observed in interplanetary space on Pioneer 10 as it approached within 1 AU of Jupiter. These discrete bursts or increases were typically several hundred times the normal quiet-time electron flux and became much more frequent with decreasing distance to Jupiter, the result being the quasi-continuous presence of large fluxes of these electrons in interplanetary space. In view of the likely origin of these electrons at Jupiter and the similarity of these increases to quiet-time electron increases previously observed at earth, the temporal presence of the quiet-time increases has been reexamined. It is found that these increases have a 13-month periodicity, indicating a Jovian origin for the events near the earth as well. It is noted that the integrated flux from quiet-time increase electrons at 1 AU is comparable to the integrated ambient electron flux itself.

Teegarden, B. J.↗
NASA NTRS1974

The variation of solar proton energy spectra size distribution with heliolongitude

A statistical study of the initial phases of 185 solar particle events was carried out using the data from cosmic ray experiments on IMP 4 and IMP 5. Special emphasis was placed on the identification of the associated solar flare, as the parent flare can be determined for 68% of the events. It appears probable that most of the unidentified increases occur on the non-visible disc of the sun. The existence of a 'preferred-connection' longitude between 20 W and 80 W was established by examining the heliolongitude of all the flare associated events. It is demonstrated that the energy spectra determined at the time of maximum particle in the 20 to 80 MeV or 4 to 20 Mev interval range give results identical to that obtained by the 'distance-travelled' method.

Vanhollebeke, M. A. I.↗
NASA NTRS1974

Energetic particles in the Jovian magnetosphere

A detailed account of the Pioneer 10 encounter with Jupiter is presented. Flux time histories of electrons and protons are given over a wide energy band. Proton and electron energy spectra are given at various Jovicentric distances. Proton spectra are shown to transform from a power law with indices in the 3-4.2 range to more nearly exponential forms in the inner regions. Extensive data are presented on the angular distributions of protons and electrons at various locations in the Jovicentric magnetosphere. In addition, a harmonic analysis of 1-2 MeV proton angular distributions was performed. Alpha/proton ratios are given as a function of Jovian radius and are compared to the earth and solar wind values.

Trainor, J. H.↗
NASA NTRS1974

The anomalous abundance of cosmic-ray nitrogen and oxygen nuclei at low energies

Recent measurements using the Goddard-University of New Hampshire cosmic-ray telescope on the Pioneer 10 spacecraft have revealed an anomalous spectrum of nitrogen and oxygen nuclei relative to other nuclei such as He and C, in the energy range 3-30 MeV per nucleon. The intensity of nitrogen and oxygen nuclei is enhanced by a factor of up to 20 relative to their abundance in galactic or solar cosmic rays. It is argued that this is most likely a new extrasolar component of cosmic rays.

Mcdonald, F. B.↗
NASA NTRS1974

Energetic particle population in the Jovian magnetosphere - A preliminary note

Preliminary account of energetic particle measurements conducted by the Pioneer 10 spacecraft during approach to Jupiter in November and December 1973. Graphs illustrate electron and proton flux levels as a function of distance from the planet for different particle energy intervals. Times of predicted equatorial crossing are marked along with positions corresponding to the bowshock, magnetopause, and other features. The general patterns of particle distribution in the Jovian vicinity are discussed.

Trainor, J. H.↗
NASA NTRS1974

A catalogue of solar cosmic ray events: IMPS 4 and 5, May 1967 - December 1972

This catalogue of solar cosmic ray events has been prepared for the use of solar physicists and other interested scientists. It contains some 185 solar particle events detected by the Goddard Space Flight Center Cosmic Ray Experiments on IMP's IV and V (Explorer 34 and 41) for the period May 1967 - December 1972. The data is presented in the form of hourly averages for three proton energy intervals - 0.9 - 1.6 MeV; 6 - 20 MeV and 20 - 80 MeV. In addition the time histories of .5 - 1.1 MeV electrons are shown on a separate scale. To assist in the identification of related solar events, the onset time of the electron event is indicated. The details of the instrumentation and detector techniques are described. Further descriptions of data reduction procedure and on the time-history plots are given.

Vanhollebeke, M. A.↗
NASA NTRS1974

Interplanetary MeV electrons of Jovian origin

Observations of low energy electron increases observed in interplanetary space on Pioneer 10 are reported as it approached Jupiter. These discrete bursts were several hundred times the normal quiet-time electron flux, and became more frequent as one approached Jupiter resulting in the quasi-continuous presence of large fluxes of these electrons in interplanetary space. It is noted that the integrated flux from quiet-time electrons is comparable to the integrated ambient electron flux itself. In addition, the spectrum of electrons observed in Jupiter's magnetosphere, on Pioneer 10 in interplanetary space near Jupiter, for the quiet-time increases near the earth, and for the ambient electron spectrum are all remarkably similar. These two lines of evidence suggest the possibility that Jupiter could be the source of most of the ambient electrons at low energies.

Teegarden, B. J.↗
NASA NTRS1974

The modulation of low energy galactic cosmic rays

It has been clearly established by several different experiments that following the last solar maximum (about 1969), there was a significant phase lag or hysteresis effect between changes in the low rigidity galactic cosmic rays and the high rigidity components. It was possible to explain this in terms of the diffusion-convection-modulation theory by varying either the diffusion coefficient or the size of the modulation region as a function of time. During the ensuing recovery phase of the solar modulated spectra, at the mid point toward the minimum of the solar activity, new striking features have been observed, and these new observations are discussed.

Van Hollebeke, M. A. I.↗
NASA NTRS1974

High energy particles and quanta in astrophysics

The various subdisciplines of high-energy astrophysics are surveyed in a series of articles which attempt to give an overall view of the subject as a whole by emphasizing the basic physics common to all fields in which high-energy particles and quanta play a role. Successive chapters cover cosmic ray experimental observations, the abundances of nuclei in the cosmic radiation, cosmic electrons, solar modulation, solar particles (observation, relationship to the sun acceleration, interplanetary medium), radio astronomy, galactic X-ray sources, the cosmic X-ray background, and gamma ray astronomy. Individual items are announced in this issue.

Mcdonald, F. B.↗
NASA NTRS1974

Cosmic ray experimental observations

The current experimental situation in cosmic ray studies is discussed, with special emphasis on the development of new detector systems. Topics covered are the techniques for particle identification, energy measurements, gas Cerenkov counters, magnet spectrometers, ionization spectrometers, track detectors, nuclear emulsions, multiparameter analysis using arrays of detectors, the Goddard ionization spectrometer, charge spectra, relative abundances, isotope composition, antinuclei in cosmic rays, electrons, the measurement of cosmic ray arrival directions, and the prehistory of cosmic rays.

Balasubrahmanyan, V. K.↗
NASA NTRS1974

Solar particles /observations, relationship to the sun acceleration, interplanetary medium/

The major features of the propagation of flare particles in the interplanetary medium are discussed in terms of the classic well-behaved flare having unique impulsive injection and a smooth time profile. Topics include flare events, their frequency of occurrence, development of a typical event, energy spectra, proton and electron types, charge and isotopic composition, solar flares and particle accelerations, radio and X-ray observations, the Fermi mechanism, the betatron mechanism, acceleration models, plasma instabilities, two-stage acceleration, propagation mechanisms, the anisotropic stage, the diffusive stage, and the convection and energy loss stage.

Mcdonald, F. B.↗