Isotopic Fractionation by Plasma Processes |
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Authors: | Kallenbach Reinald |
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Institution: | (1) International Space Science Institute, Hallerstr. 6, CH-3012 Bern, Switzerland |
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Abstract: | The Sun is the largest reservoir of matter in the solar system, which formed 4.6 Gy ago from the protosolar nebula. The solar
wind carries a nearly unfractionated sample of heavy isotopes at energies of about 1 keV/amu from the Sun into interplanetary
space. Data from space missions and theoretical models indicate that the isotopes of the volatile elements N, O, Ne, and Ar
are fractionated by at most a few percent per atomic mass unit in different solar wind regimes. In contrast, isotopic abundances
of solar and heliospheric energetic particles at energies larger than about 100 keV/amu are observed to strongly vary relative
to solar abundances. Processes such as resonant acceleration or pre-acceleration by plasma waves, first-order Fermi acceleration,
or propagation in the interplanetary plasma are discussed as causes for charge-to-mass dependent fractionation.
This revised version was published online in August 2006 with corrections to the Cover Date. |
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