Abstract/Details

A search for thermospheric composition perturbations due to vertical winds


2006 2006

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Abstract (summary)

The thermosphere is generally in hydrostatic equilibrium, with winds blowing horizontally along stratified constant-pressure surfaces, driven by the dayside-to-nightside pressure gradient. A marked change in this paradigm resulted after Spencer et al. [1976] reported vertical wind measurements of 80 m·s-1 from analyses of AE-C satellite data. It is now established that the thermosphere routinely supports large-magnitude (∼30-150 m·s-1) vertical winds at auroral latitudes. These vertical winds represent significant departure from hydrostatic and diffusive equilibrium, altering locally---and potentially globally---the thermosphere's and ionosphere's composition, chemistry, thermodynamics and energy budget. Because of their localized nature, large-magnitude vertical wind effects are not entirely known.

This thesis presents ground-based Fabry-Perot Spectrometer OI(630.0)-nm observations of upper-thermospheric vertical winds obtained at Inuvik, NT, Canada and Poker Flat, AK. The wind measurements are compared with vertical displacement estimates at ∼104 km2 horizontal spatial scales determined from a new modification to the electron transport code of Lummerzheim and Lilensten [1994] as applied to FUV-wavelength observations by POLAR spacecraft's Ultraviolet Imager [Torr et al. , 1995]. The modification, referred to as the column shift, simulates vertical wind effects such as neutral transport and disruption of diffusive equilibrium by vertically displacing the Hedin [1991] MSIS-90 [O2]/[N2] and [O]/([N2]+[O2]) mixing ratios and subsequently redistributing the O, O2, and N 2 densities used in the transport code. Column shift estimates are inferred from comparisons of UVI OI(135.6)-nm auroral observations to their corresponding modeled emission. The modeled OI(135.6)-nm brightness is determined from the modeled thermospheric response to electron precipitation and estimations of the energy flux and characteristic energy of the precipitation, which are inferred from UVI-observed Lyman-Birge-Hopfield N2 emissions in two wavelength ranges. Two-dimensional column shift maps identify the spatial morphology of thermospheric composition perturbations associated with auroral forms relative to the model thermosphere. Case-study examples and statistical analyses of the column shift data sets indicate that column shifts can be attributed to vertical winds. Unanticipated limitations associated with modeling of the OI(135.6)-nm auroral emission make absolute column shift estimates indeterminate. Insufficient knowledge of thermospheric air-parcel time histories hinders interpretations of point-to-point time series comparisons between column shifts and vertical winds.

Indexing (details)


Subject
Atmosphere;
Optics
Classification
0608: Atmosphere
0752: Optics
0725: Atmosphere
Identifier / keyword
Pure sciences; Earth sciences; Auroral latitudes; Space physics; Thermospheric; Vertical winds
Title
A search for thermospheric composition perturbations due to vertical winds
Author
Krynicki, Matthew P.
Number of pages
378
Publication year
2006
Degree date
2006
School code
0006
Source
DAI-B 67/08, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9780542834271
Advisor
Conde, Mark
University/institution
University of Alaska Fairbanks
University location
United States -- Alaska
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3229738
ProQuest document ID
305353733
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/305353733
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