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Noble gas elemental abundances in three solar wind regimes as recorded by the Genesis mission

Vogel, Nadia and Heber, Veronika S. and Bochsler, Peter and Burnett, Donald S. and Maden, Colin and Wieler, Rainer (2019) Noble gas elemental abundances in three solar wind regimes as recorded by the Genesis mission. Geochimica et Cosmochimica Acta, 263 . pp. 182-194. ISSN 0016-7037. doi:10.1016/j.gca.2019.08.007.

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We discuss elemental abundances of noble gases in targets exposed to the solar wind (SW) onboard the “Genesis” mission during the three different SW “regimes”: “Slow” (interstream, IS) wind, “Fast” (coronal hole, CH) wind and solar wind related to coronal mass ejections (CME). To this end we first present new Ar, Kr, and Xe elemental abundance data in Si targets sampling the different regimes. We also discuss He, Ne, and Ar elemental and isotopic abundances obtained on Genesis regime targets partly published previously. Average Kr/Ar ratios for all three regimes are identical to each other within their uncertainties of about 1% with one exception: the Fast SW has a 12% lower Xe/Ar ratio than do the other two regimes. In contrast, the He/Ar and Ne/Ar ratios in the CME targets are higher by more than 20% and 10%, respectively, than the corresponding Fast and Slow SW values, which among themselves vary by no more than 2–4%. Earlier observations on lunar samples and Genesis targets sampling bulk SW wind had shown that Xe, with a first ionisation potential (FIP) of ∼12 eV, is enriched by about a factor of two in the bulk solar wind over Ar and Kr compared to photospheric abundances, similar to many “low FIP” elements with a FIP less than ∼10 eV. This behaviour of the “high FIP” element Xe was not easily explained, also because it has a Coulomb drag factor suggesting a relatively inefficient feeding into the SW acceleration region and hence a depletion relative to other high FIP elements such as Kr and Ar. The about 12% lower enrichment of Xe in Genesis’ Fast SW regime observed here is, however, in line with the hypothesis that the depletion of Xe in the SW due to the Coulomb drag effect is overcompensated as a result of the relatively short ionisation time of Xe in the ion-neutral separation region in the solar chromosphere. We will also discuss the rather surprising fact that He and Ne in CME targets are quite substantially enriched (by 20% and 10%, respectively) relative to the other solar wind regimes, but that this enrichment is not accompanied by an isotopic fractionation. The Ne isotopic data in CMEs are consistent with a previous hypothesis that isotopic fractionation in the solar wind is mass-dependent.

Item Type:Article
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URLURL TypeDescription
Burnett, Donald S.0000-0001-9521-8675
Maden, Colin0000-0002-6644-9535
Wieler, Rainer0000-0001-5666-7494
Additional Information:© 2019 Elsevier Ltd. Received 22 January 2019, Accepted 7 August 2019, Available online 16 August 2019. We appreciate the great support of the Genesis curation team at the Johnson Space Center, Houston with sample selection and cleaning. Heinrich Baur, Henner Busemann and Rosmarie Neukomm are thanked for technical support and discussions, and we acknowledge the very helpful comments by AE Gregory Herzog and three reviewers. This work was supported by the Swiss National Science Foundation.
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Swiss National Science Foundation (SNSF)UNSPECIFIED
Record Number:CaltechAUTHORS:20190819-104728104
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Official Citation:Nadia Vogel, Veronika S. Heber, Peter Bochsler, Donald S. Burnett, Colin Maden, Rainer Wieler, Noble gas elemental abundances in three solar wind regimes as recorded by the Genesis mission, Geochimica et Cosmochimica Acta, Volume 263, 2019, Pages 182-194, ISSN 0016-7037, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:97997
Deposited By: Tony Diaz
Deposited On:19 Aug 2019 20:29
Last Modified:16 Nov 2021 17:35

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