ProQuest
Abstract/Details

Absolute wind measurements in the lower thermosphere of Venus using infrared heterodyne spectroscopy

Goldstein, Jeffrey Jay.   University of Pennsylvania ProQuest Dissertations & Theses,  1989. 9015098.

Abstract (summary)

The first absolute wind velocities above the cloud-tops were obtained using NASA/Goddard Space Flight Center infrared heterodyne spectrometers at the NASA IRTF and the McMath Solar Telescope, December 1985 to March 1987, during four planetary phases spanning 82% of a synodic period. Bean-integrated Doppler displacements in the non-thermal emission core of $\sp{12}{\rm C}\sp{16}{\rm O}\sb2$ 10.33 $\mu$m R(8) (obtained at sub-Doppler resolution: $\lambda/\Delta\lambda$ = 10$\sp7$), sampled the line of sight projection of the lower thermospheric wind field (100-120 km). A field-usable Lamb-dip laser stabilization system, developed for spectrometer absolute frequency calibration to $<$ $\pm$ 0.1 MHz, allowed S/N-limited line of sight velocity resolution at the 1 m/s level. The spectrometer's diffraction-limited beam (1.7 arc-second HPBW at McMath, 0.9 arc-second HPBW at IRTF), and 1-2 arc-second seeing, provided the spatial resolution necessary for circulation model discrimination. Qualitative analysis of beam-integrated winds definitively established a dominant subsolar-antisolar circulation in the lower thermosphere. A retrograde zonal component was also suggested. Beam-integrated winds were modelled with a 100 x 100 grid over the beam, incorporating beam spatial rolloff and across-the-beam gradients in non-thermal emission intensity, line of sight projection geometry, and horizontal wind velocity. Horizontal wind velocity was derived from a 2-parameter model wind field comprised of subsolar-antisolar and zonal components. Best-fit models indicated a dominant subsolar-antisolar flow with 120 m/s cross-terminator winds and a retrograde zonal component with a 25 m/s equatorial velocity (assuming wind field temporal stability over the synodic period). The subsolar-antisolar component is consistent with the Bougher et al. (1986) 2-dimensional hydrodynamical model for 110 km. Detection of a significant zonal component indicates upper thermospheric super-rotation may be coupled to, hence pumped by, cloud level super-rotation. Early heterodyne mesospheric wind measurements (Betz et al. 1977b) were re-examined based on laser stability test results. A reinterpretation is consistent with superposition of a 94 $\pm$ 6 m/s zonal super-rotation and a 35 $\pm$ 6 m/s antisolar-subsolar return flow at $\sim$75 km. A review of all dynamical indicators above the cloud-tops allowed development of an integrated and self-consistent picture of circulation in the 70-200 km range. Finally, historical visual observations of solar phase-locked structure were reviewed and discussed in light of the heterodyne results.

Indexing (details)


Subject
Astronomy;
Astrophysics;
Atmosphere;
Molecules
Classification
0606: Astronomy
0609: Molecular physics
0725: Atmospheric sciences
Identifier / keyword
Pure sciences
Title
Absolute wind measurements in the lower thermosphere of Venus using infrared heterodyne spectroscopy
Author
Goldstein, Jeffrey Jay
Number of pages
430
Degree date
1989
School code
0175
Source
DAI-B 51/01, Dissertation Abstracts International
ISBN
979-8-207-34405-8
Advisor
Shen, Benjamin S. P.; Mumma, Michael J.
University/institution
University of Pennsylvania
University location
United States -- Pennsylvania
Degree
Ph.D.
Source type
Dissertation or Thesis
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
9015098
ProQuest document ID
303783844
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
https://www.proquest.com/pqdtglobal/docview/303783844/