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  • 1
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Recently synthesized (t≲109 yr)r-process material has actinide elemental and isotopic abundance characteristics which can be used to distinguish it from ancientr-process material. The time-dependence of relative actinide abundances provides detailed chronometric information. Also it is shown that, ifN=184 is a neutron magic number as predicted by nuclear thery, the resultingr-process production peak atA∼281 will in turn yield, due to symmetric fission, a broad abundance peak aroundA∼135–140. The present results can be used to help verify or refute some current hypotheses concerning the origin of UH cosmic rays and some of the abundance anomalies in peculiar stars.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The origin of the elements from Cu to As in the UH (ultra-heavy) cosmic rays is investigated and related to current concepts of the nucleosynthesis of solar system material. The charge spectrum of the UH cosmic rays in the interval 29≤Z≤60 is studied via a fully developed propagation calculation for source abundances given by solar system material, ther-process, the massive-star core helium-burnings-process, and explosive carbon burning. None of these sources considered individually can explain the cosmic ray observations. However a combination of material produced in ther-process, the core helium-burnings-process and in explosive carbon burning provides a good representation of the experimental data. The cosmic-rayr-process is found to differ from solar systemr-process events by an underproduction of the low-massr-process peaks relative to theA∼195 peak. The large cosmicray abundance forZ=40–44 may be due to anr-process fission component, but this explanation is by no means certain. Improved cosmic-ray data, especially for Zn−Sr, can provide limits to the various source contributions. The model described here gives a consistent picture for the origin of both the cosmic rays and the solar system elements just beyond iron, and adds additional evidence for the importance of massive stars as a site of nucleosynthesis and the birthplace of the cosmic rays.
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  • 3
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The RAPID spectrometer (Research with Adaptive Particle Imaging Detectors) for the Cluster mission is an advanced particle detector for the analysis of suprathermal plasma distributions in the energy range from 20–400 keV for electrons, 40 keV–1500 keV (4000 keV) for hydrogen, and 10 keV nucl-1–1500 keV (4000 keV) for heavier ions. Novel detector concepts in combination with pin-hole acceptance allow the measurement of angular distributions over a range of 180° in polar angle for either species. Identification of the ionic component (particle mass A) is based on a two-dimensional analysis of the particle's velocity and energy. Electrons are identified by the well-known energy-range relationship. Details of the detection techniques and in-orbit operations are described. Scientific objectives of this investigation are highlighted by the discussion of selected critical issues in geospace.
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  • 4
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The ‘EPAC’ instrument on Ulysses is sensitive to relativistic cosmic rays when far from Jupiter and in the absence of energetic solar particles. Measurement of the latitude gradient of these particles, after correction for time variations, has been made for the 1993–1994 south polar pass. The average magnitude of the gradient is about the same or smaller than predicted by a model which includes full gradient drift. However, the latitude dependence of the solar plasma output into interplanetary space (including fast-stream and magnetic turbulence effects) seems to be important in determining the magnitude of modulation.
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  • 5
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The CEPPAD Experiment consists of four sensors for investigating energetic particle phenomena on the POLAR mission. These sensors provide 3-D proton and electron angular distributions in the energy range of 20 keV to 1 MeV, energetic proton and electron measurements extending to energies greater than 10 MEV, high angular and time resolution measurements in the loss-cone, and data on energetic neutral particles. All sensors operate in conjunction with special on-board data processing units which control sensor data acquisition modes while performing in-flight data processing, data compression, and telemetry formatting. Presented here is a CEPPAD system overview together with descriptions of the individual sensors, the in-flight data processing, and examples of sensor calibration data.
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  • 6
    ISSN: 1572-9672
    Keywords: Energetic particles ; Ulysses ; Composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The relative abundances of low energy ions (0.6–2.0 MeV/n) in solar energetic particle (SEP) and corotating interaction region (CIR) events have been measured by the EPAC experiment aboard Ulysses since launch in October 1990 until the present time. We give an overview of the abundances of heavy ions (He, C, Ne, Fe) relative to oxygen during energetic particle events lasting longer than 5 days during the in- and out-of-ecliptic phase of the mission. While the period Oct. 1990 to Aug. 1992 was dominated by high solar activity the Ulysses out of ecliptic passage at solar latitudes up to 45° went parallel to the declining phase of solar activity. Thus a very clear structure of corotating interaction regions was observed. While the in-ecliptic composition is in general agreement with measurements made near the Earth, the development of the CIR-composition shows two phases: From Aug. 1992 to May 1993 the C/O-ratio is 0.55–0.70, afterwards it increases to 0.8–0.9. This increase is correlated to the disappearance of the current sheet at 30° solar latitude reported by Smithet al. (1993).
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 287 (1980), S. 365-365 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] THOMAS1 has suggested that changes in the magnetic flux content of the convection zone produces changes in radius. However, his calculations did not include the effect of structural changes in the superadiabatic region on the bulk of the convection zone. Theoretical studies2'4 have shown that solar ...
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  • 8
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 263 (1976), S. 707-708 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] BLACK1 has suggested that the anomalous Xe isotopic composition known as carbonaceous chondrite fission (CCF) Xe results from a varient of the r-process and is not due to fission. To yield the CCF Xe isotopic composition, the r-process peak due to the neutron magic number 82 would need to occur at ...
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  • 9
    Publication Date: 2011-08-19
    Description: Using electron count rate data at geostationary orbit, daily energy spectra, extending from 30 keV to 15 MeV, have been developed for trapped relativistic electrons at 6.6 earth radii. These spectra have been used to model the flux of these electrons into the atmosphere at 120 km. Energy deposition calculations permit daily sources of HO(x) and NO(y) to be calculated at auroral and subauroral latitudes due to relativistic electron precipitation (REP) for the period June 13, 1979, through June 4, 1988. Both short-term and long-term source variations are quite large over the period considered. The results suggest that a significant contribution to the anomalously large and unexplained global O3 declines between 1979 and 1985 has been made by the catalytic destruction of O3 by odd nitrogen in the lower stratosphere at mid to high latitudes. The results also provide evidence for a clear and strong linkage between solar variability, the state of the magnetosphere, and the chemical climatological state of the middle and lower atmosphere.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 2939-297
    Format: text
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  • 10
    Publication Date: 2011-08-19
    Description: Twenty-seven-day periodic enhancements of the relativistic electrons are observed in association with concurrently measured solar wind streams, and a numerical transport code is used to investigate the coupling of these high-energy electrons to earth's upper and middle atmosphere. When precipitated, these electrons are found to show a large energy deposition at 40-60 km altitude which is 3-4 orders of magnitude greater than the galactic cosmic ray or solar EUV energy deposition at these altitudes. It is suggested that this electron population could play a role in coupling solar wind and magnetospheric variability to the middle atmosphere through a modulating effect on lower D-region ionization and possibly on upper level ozone chemistry.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 14; 1027-103
    Format: text
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