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Thule Fabry-Perot


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Instrument/Model Description

The Thule Fabry Perot interferometer, operated by the Space Physics Research Laboratory, Department of Atmospheric, Oceanic and Space Sciences of the University of Michigan is located at latitude 76.53N and longitude 68.44W.

Currently, the interferometer observes the line profiles of the forbidden emissions OI (5577 A) and OI (6300 A). All the data in the CEDAR Data Base are 6300 A. The geophysical parameters obtained from the data reduction are the gas kinetic temperature of the emitting region from the natural width of the sky profile, the line of sight wind from the Doppler shift of the sky profile, and the surface brightness of the emission line. OI (6300 A) nightglow emission is generally believed to issue from the altitude range 175 to 500 km, with the major contribution originating from a narrow height interval (a few scale heights thick) centered roughly one neutral scale height below the altitude of maximum electron density. Thus, the peak altitude of emission and the parameters of the F region are interdependent and it is difficult to assign a unique altitude to each ground based OI (6300 A) interferometer measurement. If no other information is available, we generally ascribe 250 km as the altitude of emission.

Line of sight winds derived from the observed shift of the emission line from a zero reference position requires the determination of a zero wind. The reference zero wind is taken to be the average of an entire nights vertical wind data. Generally, the four cardinal directions are also sampled as well as the vertical. There is no exclusion of any data in the CEDAR Data Base, so cloudy night fits are also included. The cloud cover (code 440) measured by the Thule meteorological station is given in octas of the sky covered. Values range from 0 (clear) to 9 (overcast). In the summary plots, wind measurements were not plotted unless the cloud cover was 0-3. Temperatures and relative emission measurements were not plotted unless the cloud cover was 0-6. For periods where there are plots of the vertical wind, but not of the horizontal wind, then the look directions are not cardinal. Line-of-sight winds are available, but further assumptions and a combination of look directions must be used to compute the cardinal horizontal winds. For the period of data in the CEDAR Data Base, the cloud cover was 0-3 100% of the time so all data points were plotted

References for the instrument and data processing procedures

Killeen et al., Appl. Opt. 23, 612 (1984)
McCormac et al., Planet. Space Sci. 35, 1255 (1987)
Meriwether et al., Opt. Eng. 22, 128 (1983)
Niciejewski et al., SPIE Proceedings, 1745, 165 (1992)

Summary Plots for Thule Fabry-Perot in OI (6300 A)

-Revised 22 June 2000 by Barbara Emery