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  • 1
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    The cosmic-ray spectra of H-1, H-2, and He-4 as a test of the origin of the hydrogen superfluxes at solar minimum modulation (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Low-energy 1-AU cosmic-ray spectra obtained using the IMP-8 satellite cosmic-ray telescope (Garcia-Munoz et al., 1975) at quiet times during the solar minimum of 1972-1977 are reported and combined with published data on that minimum and the previous one (1965), with a focus on the anomalous He-4 and heavy-nucleus spectra and proton and helium superfluxes observed in 1972-1977. The 56-MeV/nucleon H-2/H-1 and H-2/He-4 abundance ratios and the differential energy spectra are plotted versus time and solar modulation level over an entire cycle, and the proton and He superfluxes, which do not contribute to the anomalies, are attributed to the reduced levels of residual modulation present during 1972-1977.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 294; 455-462
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  • 2
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    The heliospheric intensity gradients of the anomalous He4 and the galactic cosmic-ray components (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Measurements made with Pioneers 10 and 11 over the radial range of 1 to about 25 AU from 1972 to 1981 are presented to show that at solar minimum (1972-1977), the radial gradient for the anomalous helium component from 11 to 20 MeV/n is about 14%/AU. This result is significantly smaller than that predicted for either charge state of the component based on the observed spectrum and assumptions of conventional solar modulation for particles propagating inward from the heliospheric boundary. It is confirmed that the solar modulation mechanism that determines the level and distribution of low-energy galactic cosmic rays in the heliosphere, also modulates the He(A) spectrum. With increasing modulation between solar minimum and maximum, the 10-20 MeV/n He(A) flux decreases below the flux of modulated galactic He first at 1 AU and then progressively outward to 22-25 AU over an approximately two year period.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 257
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  • 3
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    Trajectory-capture cell instrumentation for measurement of dust particle mass, velocity and trajectory, and particle capture (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The development of the polyvinylidene fluoride (PVDF) dust detector for space missions--such as the Halley Comet Missions where the impact velocity was very high as well as for missions where the impact velocity is low was extended to include: (1) the capability for impact position determination - i.e., x,y coordinate of impact; and (2) the capability for particle velocity determination using two thin PVDF sensors spaced a given distance apart - i.e., by time-of-flight. These developments have led to space flight instrumentation for recovery-type missions, which will measure the masses (sizes), fluxes and trajectories of incoming dust particles and will capture the dust material in a form suitable for later Earth-based laboratory measurements. These laboratory measurements would determine the elemental, isotopic and mineralogical properties of the captured dust and relate these to possible sources of the dust material (i.e., comets, asteroids), using the trajectory information. The instrumentation described here has the unique advantages of providing both orbital characteristics and physical and chemical properties--as well as possible origin--of incoming dust.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Workshop on Analysis of Returned Comet Nucleus Samples; p 64-65
    Format: application/pdf
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  • 4
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    The Jovian relativistic electron distribution in interplanetary space from 1 to 11 AU - Evidence for a continuously emitting 'point' source (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: From observations of Jovian electrons with instrumentation on the Pioneer 10 spacecraft, it is concluded from both their spatial distribution and their modulation in interplanetary space by solar corotating interaction regions (CIRs) that, whatever the scale size of the Jovian magnetotail, the escape of relativistic electrons occurs within 1 AU of the planet. Thus, on the large scale of the heliosphere, Jupiter appears as a continuously emitting 'point source'. The close approach of the spacecraft at 9.6 AU to a possible extension of a magnetotail early in 1976 is discussed. From recurring intensity increases of approximately 1-MeV protons, it is concluded that CIRs have not dissipated even at about 11 AU.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 215
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  • 5
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    Observations of Jovian electrons at 1 AU throughout the 13 month Jovian synodic year (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A study of Jovian electron-flux increases observed aboard the IMP-8 earth-orbiting satellite reveals that, contrary to previous reports of a 4-8-month Jovian electron 'season', Jovian electron-intensity increases were observed almost continuously from late 1973 into 1976, with peak intensities occurring at times of best connection between earth and Jupiter along the average direction of the interplanetary magnetic field about every 13 months. These observations are consistent with Jovian electron propagation both along and across the direction of the average interplanetary magnetic field. A convection-diffusion model for Jovian electron propagation, which assumes that Jupiter is a continuously emitting point source of electrons, originally developed to explain the distribution of Jovian electrons observed on the Pioneer 10 and 11 spacecraft, can account also for the distribution of Jovian electrons observed at the orbit of earth.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal
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  • 6
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    Jovian electron propagation in three dimensions of the heliosphere: The Ulysses investigations (1993)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: We report investigations of Jovian relativistic electrons in the interplanetary medium that provide new insights into both the physical processes by which the Jovian magnetosphere releases its trapped, relativistic electrons into the interplanetary medium, and the modes of their interplanetary propagation. These studies were dependent on the unique postencounter trajectory for Ulysses. The spacecraft remained close to the radial distance of Jupiter (approximately 5.2 AU) and moved southward on the duskside by only approximately 12 deg in heliographic latitude and less than 8 deg in the heliographic azimuth relative to Jupiter for the period of approximately 100 deg days of this study. During this period the nominal Parker spiral interplanetary magnetic field with its alternating polarities sector structure established direct magnetic field line connections frequently between Jupiter and the spacecraft. These unique conditions made it possible to investigate in detail, for approximately four solar rotations, both the Jovian electron burst phenomenon and the continuous, diffusive interplanetary propagation of Jovian electrons.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 98; A12; p. 21,129-21,144
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  • 7
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    Origins of the low energy relativistic interplanetary electrons (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Electron measurements in the energy range 2-25 MeV on the Pioneer 10 spacecraft are studied from 1 to 21.5 AU. It is found that in this radial range, interplanetary low energy electron fluxes are of Jovian origin, based on the decreasing electron intensity from about 6 to 21.5 AU, a negative gradient from about 11 to 21.5 AU, and the constant spectral index observed from 1 to 21.5 AU. The upper limit of the galactic flux is estimated at 12 MeV and standard assumptions are applied to solar modulation. It is found that at 1 AU, the expected flux of galactic origin is a factor 300 or more below the observed quiet time flux, and the extrapolated interstellar flux level is consistent with estimates based on galactic diffuse radio and gamma-ray emissions.
    Keywords: ASTROPHYSICS
    Type: International Cosmic Ray Conference; Jul 13, 1981 - Jul 25, 1981; Paris; France
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  • 8
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    Confirmation of dust clusters in the coma of Comet Halley (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Measurements from the Ducma dust counter and mass analyzer on the Vega spacecraft are compared with those from the SP-1 sensor on the same spacecraft. It is shown that the sequence of pulses recorded by the SP-1 instruments show deviations from a random distribution. Some of the nonrandom sequences observed by SP-1 are in the same time intervals as the clusters observed by the Ducma instrument. The results support the analysis of Ducma data which showed highly structured variations of dust intensity through the coma and large fluxes of low mass particles extending to great distances beyond the coma (Simpson et al., 1986).
    Keywords: ASTROPHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 9; 3 19
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  • 9
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    Dust counter and mass analyser (DUCMA) measurements of comet Halley's coma from Vega spacecraft (1986)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Measurements of dust particles in comet Halley's coma from Vega spacecraft made with instruments using a new principle of dust detection and having a high time resolution over a large range of dust fluxes and masses are reported. The dust coma, whether quiescent (as seen by Vega 2) or containing a major jet structure, (as seen by Vega 1) displays large, short-term variations throughout which are at times quasi-periodic. The integral mass spectra increase in intensity to the lowest masses measured, and the flux levels lie approximately in the ranges estimated previously from ground-based observations. The coma is highly dynamical on all spatial and temporal scales, suggesting a complex structure of localized regions of dust emission from the nucleus.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 321; 278-280
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  • 10
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    The dust coma of comet P/Halley - Measurements on the Vega-1 and Vega-2 spacecraft (1987)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Measurements obtained with the Dust Counter and Mass Analyzer instruments on the Vega 1 and 2 spacecraft are used to study properties of the coma of comet P/Halley. Well-defined envelope boundaries for the inverse square dependence of flux with distance from the nucleus are found, and regions of enhanced fluxes above these R exp -2 baselines inside these boundaries are identified as dust jets. The mass spectrum of the giant flux enhancement noted near the closest approach of Vega 1 is shown to be similar to the preencounter spectra. The data suggest the emission from the nucleus of large conglomerates of small particles which disintegrate as they travel outward, explaining the 10 to the -13th g particles observed beyond the envelope boundaries.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 187; 1-2; 742-752
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