Absolute wind measurements in the lower thermosphere of Venus using infrared heterodyne spectroscopy
The first absolute wind velocities above the cloud-tops were obtained during four planetary phases spanning 82 percent of a synodic period. Bean-integrated Doppler displacements in the non-thermal emission core of (12)C(16)O2 10.33 microns R(8) (obtained at sub-Doppler resolution), sampled the line of sight projection of the lower thermospheric wind field (100 to 120 km). A field-usable Lamb-dip laser stabilization system, developed for spectrometer absolute frequency calibration to less than +/- 0.1 MHz, allowed S/N-limited line of sight velocity resolution at the 1 m/s level. The spectrometer's diffraction-limited beam 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. 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 were re-examined based on laser stability test results.
- Research Organization:
- Pennsylvania Univ., Philadelphia, PA (USA)
- OSTI ID:
- 6313413
- Resource Relation:
- Other Information: Ph.D. Thesis
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
VENUS PLANET
WIND
ATMOSPHERIC CIRCULATION
CARBON DIOXIDE
EMISSION SPECTRA
EXPERIMENTAL DATA
INFRARED SPECTRA
PLANETARY ATMOSPHERES
ATMOSPHERES
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
DATA
INFORMATION
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PLANETS
SPECTRA
640107* - Astrophysics & Cosmology- Planetary Phenomena