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  • Space Radiation  (2)
  • GEOPHYSICS  (1)
  • 1
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    Evidence for COMPTEL detections of low-energy gamma rays from HVC complexes (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Observational evidence of extended MeV emissions that may be associated with high velocity clouds (HVCs) is reported on. Based on observations acquired between 1991 and 1996 with the Compton telescope (COMPTEL), evidence is found for intense gamma ray radiation at 0.75 to 3 MeV from the general direction of two HVC regions. One bright gamma ray excess is located between the HVC complexes M and A, adjacent to the Lockman hole and is seen to approximately cover a sky area of exceptionally low H I column densities. A second source is detected at the high velocity end of complex C near the Draco Nebula. Both gamma ray excesses appear to consist of a time variable source and a diffuse emission component. The enhanced diffuse soft X-rays seen by Rosat from both HVC regions may be closely related to the gamma ray emission in terms of bremsstrahlung arising from HVC interactions with the galactic disk or lower halo.
    Keywords: Space Radiation
    Type: Proceedings of 2nd INTEGRAL Workshop 'The Transparent Universe'; 119-122; ESA-SP-382
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    INTEGRAL/SPI Observations of Electron-Positron Annihilation Radiation from our Galaxy (2005)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: The spectrometer on INTEGRAL (SPI) is a coded-aperture gamma-ray telescope with moderate angular resolution (3 deg) and superior energy resolution (2 keV at 511 kev). One of it's principal science goals is the detailed study of 511 keV electron-positron annihilation from our Galaxy. The origin of this radiation remains a mystery, however current morphological studies suggest an older stellar population. There has also been recent speculation on the possibility of the existence of light (〈 100 MeV) dark matter particles whose annihilation or decay could produce the observed 511 keV emission. In this paper we summarize the current results from SPI, compare them with previous results and discuss their implication on possible models for the production of the annihilation radiation.
    Keywords: Space Radiation
    Type: AAS Meeting; Jan 01, 2005; San Diego, CA; United States
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    NASA TECHNICAL REPORTS
  • 3
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    Neutron measurements in near-Earth orbit with COMPTEL (1995)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The fast neutron flux in near-Earth orbit has been measured with the COMPTEL instrument on the Compton Gamma Ray Observatory (CGRO). For this measurement one of COMPTEL's seven liquid scintillator modules was used as an uncollimated neutron detector with threshold of 12.8 MeV. The measurements cover a range of 4.8 to 15.5 GV in vertical cutoff rigidity and 3 deg to 177 deg in spacecraft geocenter zenith angle. One of the measurements occurred near the minimum of the deepest Forbush decrease ever observed by ground-level neutron monitors. After correction for solar modulation, the total flux is well fitted by separable functions in rigidity and zenith angle. With the spacecraft pointed near the nadir the flux is consistent with balloon measurements of the atmospheric neutron albedo. The flux varies by about a factor of 4 between the extremes of rigidity and a factor of 2 between the extremes of zenith angle. The effect of the spacecraft mass in shielding the detector from the atmospheric neutron albedo is much more important than its role as a source of additional secondary neutrons. The neutron spectral hardness varies little with rigidity or zenith angle and lies in the range spanned by earlier atmospheric neutron albedo measurements.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 100; A7; p. 12,243-12,249
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    NASA TECHNICAL REPORTS
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