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At least 649 records · Page 36
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NASA NTRS1974

A model of the open magnetosphere

The Chapman-Ferraro image method is extended to construct an idealized model of the open magnetosphere that responds to a change of the interplanetary field direction as well as to a change of the field magnitude or of the solar wind momentum flux. The magnetopause of the present model is an infinite plane surface having a normal field component distribution that is consistent with the merging theory. An upper limit on the inward displacement of the magnetopause following a southward turning of the interplanetary field is obtained. The results are in fair agreement with a single event reported by Aubry et al. (1971). The model determines the field configuration and the total magnetic flux connecting the magnetosphere to interplanetary space.

Kan, J. R.↗
NASA NTRS1974

Coherent propagation of charged particle bunches in random magnetic fields

When the distribution function for energetic particles moving in interplanetary space is expressed in terms of eigenfunctions of an operator which describes pitch angle scattering by random magnetic fields, the familiar phenomenon of diffusion is the dominant solution of the transport equations provided that the spectrum of magnetic fluctuations is not too steep. The present paper describes a novel mode of particle transport when the latter condition is not satisfied (i.e., when the exponent for the spectrum of magnetic fluctuations is greater than 2). In this mode, the density inhomogeneities propagate coherently, in wavelike fashion, and with very little dispersion along the guiding field at a characteristic velocity equal to half the particle speed. The most striking manifestation of this phenomenon is the observed scatter-free propagation of solar flare electrons below 1 MeV.-

Earl, J. A.↗
NASA NTRS1974

Direct observations of the charge states of low energy solar particles

The charge states of carbon and oxygen of solar origin have been measured directly in interplanetary space. At 100 keV per nucleon the C(+5)/C(+6) and O(+7)/O(+8) ratios are 1.8 and 1.6, respectively. Abundance ratios of low energy heavy nuclei to He are found which are significantly larger than the corresponding photospheric values. The enhancement of O/He is 35, and both Si/He and Fe/He are overabundant by a factor of 100. To explain these observations a mechanism is proposed which first preferentially accelerates heavy ions and is followed by either storage of these ions in the coronal regions or strong adiabatic deceleration.

Gloeckler, G.↗
NASA NTRS1974

Coherent propagation of charged-particle bunches in random magnetic fields

When the distribution function for energetic particles moving in interplanetary space is expressed in terms of eigenfunctions of an operator which describes pitch-angle scattering by random magnetic fields, the familiar phenomenon of diffusion is the dominant solution of the transport equations provided that the spectrum of magnetic fluctuations is not too steep. However, if the power-versus-wavenumber spectrum of the random fields has a spectral index greater than 2, the dominant solution of the same equations is a qualitatively different mode of transport in which density inhomogeneities propagate coherently along the guiding field with a characteristic velocity equal to half the particle speed. The present work, which extends classical transport theory to give a detailed treatment of the new mode, presents explicit formulae which describe the spatial and temporal structure of the coherent disturbance. It is shown that this disturbance evolves asymptotically into a moving Gaussian pulse whose width increases with time.

Earl, J. A.↗
NASA NTRS1975

Time-dependent 2.2 MeV and 0.5 MeV lines from solar flares

The time dependences of the 2.2 MeV and 0.51 MeV gamma ray lines from solar flares are calculated and the results are compared with observations of the 1972, August 4 and 7 flares. Time lag between the nuclear reactions and the formation of these two lines are caused, respectively, by capture of the neutrons, and by deceleration of the positrons and decay of the radioactive nuclei. Results show that the calculation is consistent with the observed rise of the 2.2 MeV line on August 4, and it does not require different time dependences for the accelerated protons and electrons in the flare region. The above lags can explain the delayed gamma ray emission observed on August 7. Positrons of energies greater than about 10 MeV could be detected in interplanetary space following large solar flares.

Wang, H. T.↗
NASA NTRS1975

Aerospace Medicine and Biology: A continuing bibliography with indexes, supplement 139

The biological, physiological, psychological, and environmental effects to which man is subjected during and following simulated or actual flight in the earth's atmosphere or in interplanetary space are referenced. Similar effects on biological organisms of lower order are also included. Related topics such as sanitary problems, pharmacology, toxicology, safety and survival, life support systems, exobiology, and personnel factors are discussed. Applied research is emphasized, but references to fundamental studies and theoretical principles related to experimental development are also included. A total of 242 reports, articles, and other documents are listed.

Source record↗
NASA NTRS1975

A New Look at Jupiter: Results at the Now Frontier

Pioneer 10's encounter with Jupiter is discussed along with the interplanetary space beyond the orbit of Mars. Other topics discussed include the size of Jupiter, the Galilean satellites, the magnetic field of Jupiter, radiation belts, Jupiter's weather and interior, and future exploration possibilities. Educational projects are also included.

Source record↗
NASA NTRS1975

Aerospace Medicine and Biology: A continuing bibliography with indexes, supplement 143

This supplement to Aerospace Medicine and Biology (NASA SP-7011) lists 251 reports, articles and other documents announced during June 1975 in Scientific and Technical Aerospace Reports (STAR) or in International Aerospace Abstracts (IAA). The first issue of the bibliography was published in July 1964; since that time, monthly supplements have been issued. In its subject coverage, Aerospace Medicine and Biology concentrates on the biological, physiological, and environmental effects to which man is subjected during and following simulated or actual flight in the earth's atmosphere or in interplanetary space. References describing similar effects of biological organisms of lower order are also included. Such related topics as sanitary problems, pharmacology, toxicology, safety and survival, life support systems, exobiology, and personnel factors receive appropriate attention. In general, emphasis is placed on applied research, but references to fundamental studies and theoretical principles related to experimental development also qualify for inclusion.

Source record↗
NASA NTRS1974

Periodic escape of relativistic electrons from the Jovian magnetosphere

We adopt a model in which the Jovian magnetospheric tail is forced open by plasma that is accelerated out of the ionosphere by the centrifugal force of corotation. Any longitudinal asymmetry that exists in the ionospheric plasma source and/or the planetary magnetic field will cause a diurnal variation in the radial extent of the trapping region for energetic electrons. This diurnal variation in the extent of the particle trapping region can result in a time-dependent loss of relativistic electrons from the Jovian magnetosphere, modulated at the planetary rotation period. The diurnal trapping process may be relevant to the observation of electron pulses in interplanetary space during the Pioneer 10 approach to Jupiter.

Hill, T. W.↗
NASA NTRS1974

Intensity and energy spectrum of electrons accelerated in the earth's bow shock

Shock waves accelerate charged particles in the solar atmosphere, in interplanetary space and around the earth's magnetosphere. Acceleration of both electrons and protons occurs in the earth's bow-shock. The acceleration of protons up to 100 keV appears to be a steady state process and may even occur upstream from the bow shock due to waves generated by reflected solar wind protons. The electrons, on the other hand, are known to be accelerated in or near the shock. The intensity of these electrons ranges from about 100 to 2,000 per sr-sq cm-sec-keV at 14 keV. The energy spectrum is not a simple power low and is highly variable. If segments of the spectra are fitted to a power low, slopes ranging from -2 to -4.5 result over the energy range 0.5 to 100 keV.

Anderson, K. A.↗
NASA NTRS1974

Cosmic ray anisotropies late in a solar flare event

The detailed relationship between the anisotropy characteristics observed during late times in the decay of a solar flare event and the interplanetary magnetic field parameters is investigated. The anisotropy always is from 45 deg east of the earth-sun line. This direction is approximately perpendicular to the nominal Archimedean spiral, independent of the particle energy. The amplitude of the anisotropy increases as the magnetic field azimuthal direction shows greater departure from the radial direction. These results are discussed in terms of current ideas about solar particle propagation in the interplanetary space.

Allum, F. R.↗
NASA NTRS1975

Causes of Forbush decreases and other cosmic ray variations

The relationship between neutron monitor variations and the intensity variations of the interplanetary magnetic field is studied by using Deep River data and Imp series satellite data. In over 80% of the cases studied in 1968, identifiable depressions of the cosmic ray intensity are associated with magnetic field enhancements of several hours duration and intensity above 10 gamma. Conversely, almost every magnetic field enhancement has an identifiable effect (though not necessarily a marked depression) on the cosmic ray intensity. Perpendicular gradient drifts are suggested as one possible mechanism producing the individual decreases, and some ideas on the recovery processes are presented. Long-lasting Forbush decreases are found to be the consequence of the action of several successive magnetic field enhancements. Evidence is presented that indicates that most of these enhancements are caused by the steepening of streams in interplanetary space.

Barouch, E.↗
NASA NTRS1975

A model for the origin of solar wind stream interfaces

The basic variations in solar wind properties that have been observed at 'stream interfaces' near 1 AU are explained by a gas dynamic model in which a radially propagating stream, produced by a temperature variation in the solar envelope, steepens nonlinearly while moving through interplanetary space. The region thus identified with the stream interface separates the ambient solar wind from the fresh hot material originally in the stream. However, the interface regions given by the present model are thicker than most stream interfaces observed in the solar wind, a fact suggesting that some additional physical process may be important in determining that thickness. Variations in the density, speed, or Alfven pressure alone appear not to produce streams with such an interface.

Hundhausen, A. J.↗
NASA NTRS1975

Access of solar electrons to the polar regions

Riometric and forward-scatter radio-wave absorption measurements at high polar latitudes in both hemispheres are compared with absorption calculations based on satellite observations in the magnetosheath to determine whether a north-south asymmetry in the solar electron flux occurred during a polar-cap absorption (PCA) event. Detection of solar electrons in interplanetary space is shown to have occurred simultaneously with detection of HF radio-wave absorption, indicating that the initial stage of the PCA was due to the arrival of solar electrons. A north-south asymmetry is observed in the electron flux, and it is found that the flux precipitating over the South Pole did not exceed the mean unidirectional intensity of the electrons detected in space. The ratio between fluxes in the low and high polar latitude regions over Antarctica during a period of solar electron anisotropy is found to be comparable with that obtained during periods of isotropy. These results are shown to be consistent with the idea of an open magnetosphere and with the conclusion that an anisotropic solar electron flux may be rendered isotropic at the magnetopause.

Nielsen, E.↗
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 NTRS1976

Alternative approaches to fusion

The limitations of the Tokamak fusion reactor concept are discussed and various other fusion reactor concepts are considered that employ the containment of thermonuclear plasmas by magnetic fields (i.e., stellarators). Progress made in the containment of plasmas in toroidal devices is reported. Reactor design concepts are illustrated. The possibility of using fusion reactors as a power source in interplanetary space travel and electric power plants is briefly examined.

Roth, R. J.↗
NASA NTRS1976

Experiments out of the solar system ecliptic plane: An introduction to the ecliptic mission

Mission planning by NASA and ESA for the 1980 timeframe to observe the sun from an angle other than the solar ecliptic plane is discussed. Such missions will aid in a more thorough understanding of the sun, interplanetary space, and their influence on the earth. Jupiter swing-by techniques (first achieved by Pioneer 10) are proposed as a means of achieving an out-of-the-ecliptic mission for solar studies. Spacecraft trajectories are illustrated for a dual Pioneer spacecraft mission to observe the sun.

Simpson, J. A.↗
NASA NTRS1976

Consequences of using nonlinear particle trajectories to compute spatial diffusion coefficients

The propagation of charged particles through interstellar and interplanetary space has often been described as a random process in which the particles are scattered by ambient electromagnetic turbulence. In general, this changes both the magnitude and direction of the particles' momentum. Some situations for which scattering in direction (pitch angle) is of primary interest were studied. A perturbed orbit, resonant scattering theory for pitch-angle diffusion in magnetostatic turbulence was slightly generalized and then utilized to compute the diffusion coefficient for spatial propagation parallel to the mean magnetic field, Kappa. All divergences inherent in the quasilinear formalism when the power spectrum of the fluctuation field falls off as K to the minus Q power (Q less than 2) were removed. Various methods of computing Kappa were compared and limits on the validity of the theory discussed. For Q less than 1 or 2, the various methods give roughly comparable values of Kappa, but use of perturbed orbits systematically results in a somewhat smaller Kappa than can be obtained from quasilinear theory.

Goldstein, M. L.↗