• Narendra Bhandari

      Articles written in Journal of Earth System Science

    • Records of ancient cosmic radiation in extraterrestrial rocks

      Narendra Bhandari

      More Details Abstract Fulltext PDF

      Recent results on cosmic ray interactions in lunar samples and meteorites resulting in production of stable and radionuclides, particle tracks and thermoluminescence are reviewed. A critical examination of26A1 depth profiles in lunar rocks and soil cores, together with particle track data, enables us to determine the long term average fluxes of energetic solar protons (>10 MeV) which can be represented by (Js,Ro)=(125, 125). The lunar rock data indicate that this flux has remained constant for 5×105 to 2×106 years.

      Production rates of stable and radionuclides produced by galactic cosmic rays is given as a function of size and depth of the meteoroid. Radionuclide (53Mn,28Al) depth profiles in meteorite cores, whose preatmospheric depths are deduced from track density profiles are used to develop a general procedure for calculating isotope production rates as a function of meteoroid size. Based on the track density and22Ne/21Ne production rates, a criterion is developed to identify meteorites with multiple exposure history.22Ne/21Ne ratio <1·06 is usually indicative of deep shielded exposure. An examination of the available data suggests that the frequency of meteorites with multiple exposure history is high, at least 15% for LL, 27% for L and 31% for H chondrites. The epi-thermal and the thermal neutron density profiles in different meteorites are deduced from60Co and track density data in Dhajala, Kirin and Allende chondrites. The data show that the production profile depends sensitively on the size and the chemical composition of the meteoroid.

      Cosmic ray-induced thermoluminescence in meteorites of known preatmospheric sizes has been measured which indicates that its production profile is nearly flat and insensitive to the size of the meteoroid.

      Some new possibilities in studying cosmic ray implanted radionuclides in meteorites and lunar samples using resonance ionisation spectroscopy are discussed.

    • Records of ancient cosmic radiation in extraterrestrial rocks

      Narendra Bhandari

      More Details Abstract Fulltext PDF

      Recent results on cosmic ray interactions in lunar samples and meteorites resulting in production of stable and radionuclides, particle tracks and thermoluminescence are reviewed. A critical examination of26A1 depth profiles in lunar rocks and soil cores, together with particle track data, enables us to determine the long term average fluxes of energetic solar protons (>10 MeV) which can be represented by (Js,Ro)=(125, 125). The lunar rock data indicate that this flux has remained constant for 5×105 to 2×106 years.

      Production rates of stable and radionuclides produced by galactic cosmic rays is given as a function of size and depth of the meteoroid. Radionuclide (53Mn,26Al) depth profiles in meteorite cores, whose preatmospheric depths are deduced from track density profiles are used to develop a general procedure for calculating isotope production rates as a function of meteoroid size. Based on the track density and22Ne/21Ne production rates, a criterion is developed to identify meteorites with multiple exposure history.22Ne/21Ne ratio <1.06 is usually indicative of deep shielded exposure. An examination of the available data suggests that the frequency of meteorites with multiple exposure history is high, at least 15% for LL, 27% for L and 31% for H chondrites. The epi-thermal and the thermal neutron density profiles in different meteorites are deduced from60Co and track density data in Dhajala, Kirin and Allende chondrites. The data show that the production profile depends sensitively on the size and the chemical composition of the meteoroid.

      Cosmic ray-induced thermoluminescence in meteorites of known preatmospheric sizes has been measured which indicates that its production profile is nearly flat and insensitive to the size of the meteoroid.

      Some new possibilities in studying cosmic ray implanted radionuclides in meteorites and lunar samples using resonance ionisation spectroscopy are discussed.

    • Cosmogenic isotope and track records in meteorites and their implications to cosmic ray fluxes

      Narendra Bhandari

      More Details Abstract Fulltext PDF

      Study of several cosmic ray effects, such as VH track density, spallogenic26Al and53Mn activity,21Ne and22Ne/21Ne ratio, made in the same sample or in cores taken from different meteorites can identify parameters related to the exposure history of meteorites and cosmic ray flux variations. Meteorites with single or multiple exposure can be distinguished from a track production rate —22Ne/21Ne correlation diagram and cosmic ray flux variations over 106–107 years can be deduced from a three-isotope correlation diagram of26Al,53Mn and21Ne. Isotopic data based on chondrites with simple, one-stage exposure are consistent with the same average galactic cosmic ray intensity over the past 2 million years as that during the past 107 years.

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