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Silicon Chemistry in the Mesosphere and Lower ThermosphereSilicon is one of the most abundant elements in cosmic dust, and meteoric ablation injects a significant amount of Si into the atmosphere above 80 km. In this study, a new model for silicon chemistry in the mesosphere lower thermosphere is described, based on recent laboratory kinetic studies of Si, SiO,SiO2, and S(exp +). Electronic structure calculations and statistical rate theory are used to show that the likely fate of SiO2 is a two-step hydration to silicic acid (Si(OH)4), which then polymerizes with metal oxides and hydroxides to form meteoric smoke particles. This chemistry is then incorporated into a whole atmosphere chemistry-climate model. The vertical profiles of Si+ and the Si(exp +)Fe(exp +) ratio are shown to be in good agreement with rocket-borne mass spectrometric measurements between 90 and 110 km. Si(exp +) has consistently been observed to be the major meteoric ion around 110 km; this implies that the relative injection rate of Si from meteoric ablation, compared to metals such as Fe and Mg, is significantly larger than expected based on the irrelative chondritic abundances. Finally, the global abundances of SiO and Si(OH)4 show clear evidence of the seasonal meteoric input function, which is much less pronounced in the case of other meteoric species.
Document ID
20170003688
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Plane, John M. C. (Leeds Univ. United Kingdom)
Gomez-Martin, Juan Carlos (Leeds Univ. United Kingdom)
Feng, Wuhu (Leeds Univ. United Kingdom)
Janches, Diego (NASA Goddard Space Flight Center Greenbelt, MD United States)
Date Acquired
April 20, 2017
Publication Date
April 14, 2016
Publication Information
Publication: Journal of Geophysical Research: Atmospheres
Volume: 121
Issue: 7
ISSN: 2169-897X
Subject Category
Space Sciences (General)
Report/Patent Number
GSFC-E-DAA-TN40897
Funding Number(s)
CONTRACT_GRANT: 12-PATM12-0006
CONTRACT_GRANT: 12-PAST12-0007
Distribution Limits
Public
Copyright
Other