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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Space science reviews 78 (1996), S. 117-128 
    ISSN: 1572-9672
    Keywords: abundances ; anomalous cosmic rays ; Voyager ; interstellar medium ; heliosphere ; solar wind termination shock
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We use energy spectra of anomalous cosmic rays (ACRs) measured with the Cosmic Ray instrument on the Voyager 1 and 2 spacecraft during the period 1994/157-313 to determine several parameters of interest to heliospheric studies. We estimate that the strength of the solar wind termination shock is 2.42 (−0.08, +0.04). We determine the composition of ACRs by estimating their differential energy spectra at the shock and find the following abundance ratios: H/He = 5.6 (−0.5, +0.6), C/He = 0.00048 ± 0.00011, N/He = 0.011 ± 0.001, O/He = 0.075 ± 0.006, and Ne/He = 0.0050 ± 0.0004. We correlate our observations with those of pickup ions to deduce that the long-term ionization rate of neutral nitrogen at 1 AU is ∼ 8.3 × 10−7 s−1 and that the charge-exchange cross section for neutral N and solar wind protons is ∼ 1.0 × 10−15 cm2 at 1.1 keV. We estimate that the neutral C/He ratio in the outer heliosphere is 1.8(−0.7, +0.9) × 10−5. We also find that heavy ions are preferentially injected into the acceleration process at the termination shock.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-9672
    Keywords: abundances ; isotopes ; anomalous cosmic rays ; SAMPEX ; neon ; interstellar medium ; heliosphere ; trapped heavy ions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Measurements of the anomalous cosmic ray (ACR) isotopic composition have been made in three regions of the magnetosphere accessible from the polar Earth orbit of SAMPEX, including the interplanetary medium at high latitudes and geomagnetically trapped ACRs. At those latitudes where ACRs can penetrate the Earth's magnetic field while fully stripped galactic cosmic rays (GCRs) of similar energies are excluded, a pure ACR sample is observed to have the following composition: 15N/N 〈 0.023, 18O/16O 〈 0.0034, and 22Ne/20Ne = 0.077(+0.085, −0.023). We compare our values with those found by previous investigators and with those measured in other samples of solar and galactic material. In particular, a comparison of 22Ne/20Ne measurements from various sources implies that GCRs are not simply an accelerated sample of the local interstellar medium.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2011-08-24
    Description: The Large Isotope Spectrometer for Astromag (LISA) is an experiment designed to measure the isotopic composition and energy spectra of cosmic rays for elements extending from beryllium through zinc. The overall objectives of this investigation are to study the origin and evolution of galactic matter; the acceleration, transport, and time scales of cosmic rays in the galaxy; and search for heavy antinuclei in the cosmic radiation. To achieve these objectives, the LISA experiment will make the first identifications of individual heavy cosmic ray isotopes in the energy range from about 2.5 to 4 GeV/n where relativistic time dilation effects enhance the abundances of radioactive clocks and where the effects of solar modulation and cross-section variations are minimized. It will extend high resolution measurements of individual element abundances and their energy spectra to energies of nearly 1 TeV/n, and has the potential for discovering heavy anti-nuclei which could not have been formed except in extragalactic sources.
    Keywords: SPACE RADIATION
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  • 4
    Publication Date: 2011-08-17
    Description: The Voyager mission cosmic ray detector system, consisting entirely of solid-state charged-particle detectors, is designed to measure the energy spectrum of electrons in the range 3 to 110 MeV and the energy spectra and elemental composition of cosmic ray nuclei from hydrogen through iron in the range 1 to 500 MeV/nuc; for isotopes of hydrogen through sulfur the range is approximately 2 to 75 MeV/nuc. The cosmic ray investigation deals with the energy content, origin and acceleration process, and dynamics of cosmic rays in the galaxy, with particular attention given to low-energy phenomena in interstellar space and the outer solar system. The precise measurement of three-dimensional stream patterns of nuclei from H to Fe, as well as electrons over a wide energy range, is the data acquisition program emphasized.
    Keywords: SPACE RADIATION
    Type: Space Science Reviews; 21; Dec. 197
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  • 5
    Publication Date: 2011-08-19
    Description: The ratio of cosmic-ray source abundance to solar-system abundance for individual elements is examined. In particular correlations of these ratios with first-ionization potential (FIP) and also with the expected mass-to-charge ratio (A/Q) of the elements in a million-degree plasma are examined. The FIP correlation were previously examined and shown that the correlation is affected by the choice of C2 or C1 chondritic meteorites as the solar-system standard for comparison. An A/Q correlation was suggested by Eichler and Hainebach as a consequence of their model of shock acceleration in the hot interstellar medium, and has been examined by Israel. These correlations are presented.
    Keywords: SPACE RADIATION
    Type: Contrib. to the 19th Intern. Cosmic Ray Conf.; 4 p
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  • 6
    Publication Date: 2019-06-28
    Description: The HEAO-3 Heavy Nuclei Experiment has measured abundances of elements from Ar-18 to U-92 in the cosmic rays. The results on the ultraheavy elements, those with atomic numbers greater than 30, indicate that the source of the cosmic rays contain a mixture of r-process and s-process material similar to that found in the solar system. This result is at variance with previous indications that the sources are greatly enhanced with freshly synthesized r-process material. Apparent discrepancies between the results and the accepted solar-system abundance have led to a reexamination of data on photospheric abundances of Ge and Pb, resulting in suggested reductions in their values.
    Keywords: SPACE RADIATION
    Type: NASA Goddard Space Flight Center, Greenbelt, Md. Essays in Space Science; p 173-189
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  • 7
    Publication Date: 2019-06-28
    Description: An observation of the abundances of cosmic-ray lead and platinum-group nuclei using data from the HEAO-3 Heavy Nuclei Experiment (HNE) which consisted of ion chambers mounted on both sides of a plastic Cherenkov counter (Binns et al., 1981) is reported. Further analysis with more stringent selections, inclusion of additional data, and a calibration at the LBL Bevalac, have allowed the determination of the abundance ratio of lead and the platinum group of elements for particles that had a cutoff rigidity R(c) 5 GV. The observed ratio for Pb/Pt is distinctly lower than that predicted by any of the standard models for cosmic ray sources. It is possible that the difference is not an indication that the cosmic ray source composition is greatly different from that of the solar system, but rather that there is less Pb in the solar system and in the r-process than is assumed in the standard models.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Nineteenth International Cosmic Ray Conference. Conference Papers: Invited Rapporteur, Highlight, MIscellaneous, Volume 9; 4 p
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  • 8
    Publication Date: 2019-06-28
    Description: The Heavy Nuclei Experiment on (HEAO-3) high energy astronomy observatory 3 uses a combination of ion chambers and a Cerenkov counter. During analysis, each particle is assigned two parameters, Z sub c and Z sub i, proportional to the square roots of the Cerenkov and mean ionization signals respectively. Because the ionization signal is double valued, a unique assignment of particle charge, Z, is not possible in general. Previous work was limited to particles of either high rigidity or low energy, for which a unique charge assignment was possible, although those subsets contain less than 50% of the total number of particles observed. The maximum likelihood technique was used to determine abundances for the complete data set from approx. 1.5 to approx. 80 GeV/amu.
    Keywords: SPACE RADIATION
    Type: OG-4.4-5 , 19th Intern. Cosmic Ray Conf - Vol. 2; p 123-126; NASA-CP-2376-VOL-2
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  • 9
    Publication Date: 2019-06-28
    Description: Simultaneous magnetic field and charged particle measurements from the Voyager pacecraft at heliographic latitude separations from 10 deg to 21 deg are used to determine the latitude gradient of the galactic cosmic ray flux with respect to the interplanetary current sheet. By comparing the ratio of cosmic ray flux at Voyager 1 to that at Voyager 2 during periods when both spacecraft are first north and then south of the interplanetary current sheet, we find an estimate of the latitudinal gradient with respect to the current sheet of approximately -0.15 + or- 0.05%/deg under restricted interplanetary conditions.
    Keywords: SPACE RADIATION
    Type: SH-4.2-9 , California Inst. of Tech. Contrib. to the 19th Intern. Cosmic Ray Conf.; 4 p
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  • 10
    Publication Date: 2019-06-28
    Description: The radial gradient of anomalous O remained constant during 1977 to 85 at approximately 10 to 15%/AU although the intensity changes by more than a factor of 100. These results can be used to deduce that most of the modulation of the intensities of these particles is occurring beyond 27 AU. Evidence for a latitudinal gradient of approximately +3%/degree at low energies (7.1 to 10.6 MeV/nucl) was also found.
    Keywords: SPACE RADIATION
    Type: SH-4.6-4 , California Inst. of Tech. Contrib. to the 19th Intern. Cosmic Ray Conf.; 4 p
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