Atmospheric scattering effects on ground-based measurements of thermospheric winds

Abstract

Inherent in observations of thermospheric winds from the ground with the Fabry-Perot interferometer is the assumption that the measured Doppler shift is a property ofthe source medium viewed by the instrumental line of sight. However, ground based airglow observations in regions of weak airglow emission near large intensity gradients may be contaminated by scattered light. Light from areas where the emission is strong can be scattered by the lower atmosphere into the field of view of the observations. Thermospheric winds deduced from the observed Doppler shifts will then show apparent convergence or divergence with respect to the site of observation. Examples of this effect are found in observations by the Michigan Airglow Observatory station located near the aurora1 zone at Calgary, Alberta. Simulation calculations based upon an experimental model for a significant scattering atmosphere also showed results with either convergence or divergence in the apparent neutral wind field observed by the station.

Atmospheric scattering effects on ground‐based measurements of thermospheric vertical wind, horizontal wind, and temperature

“…This causes an apparent temperature increase from the north, where it is measured accurately, to the south, a distance of about 500 km. This result is in stark contrast with Abreu et al [], who claim that temperature measurements are unaffected by scatter. Unfortunately, this erroneous claim has been used to downplay the effects of scatter in the literature [e.g., Hernandez et al , ; Sica , ; Price et al , ].…”

“…The connection is given by (18). The optical thickness we use is smaller than the value used by Abreu et al [1983] ( 0 = 0.27), and our scattering phase function is more forward peaked.…”

Comparison of ground‐based optical observations of N2 second positive to N2+ first negative emission ratios with electron precipitation energies inferred from the Sondre Stromfjord radar

“…ASSESSING SCATTER AND EXTINCTIONEFFECTSWhen dealing with ground-based observations of auroral emissions, the effects of atmospheric scatter and extinction can be very significant. Fortunately, in the near-ultraviolet, visible, and near-infrared regions the relevant parameters are understood well enough such that models can be used to estimate the effects [e.g.,Abreu et al, 1983; Stamnes, 1986]. Using an approach similar to that ofMeier et al [1978], a model was de,reloped to investigate the magnitude of scatter and extinction at various wavelengths and for several typical auroral configurations.The model was based on the Monte-Carlo technique of following individual photons along random paths in a plane parallel atmosphere in three dimensions, from an isotropic auroral source region, through an absorbing and scattering region, until the photons were either absorbed or crossed the boundary of the assumed interaction region.…”

Thermospheric response observed over Fritz Peak, Colorado, during two large geomagnetic storms near Solar Cycle Maximum

“…The temperatures measured poleward of the station are enhanced compared with the temperatures measured in the south, indicating high-latitude heating due to auroral processes. This pattern has been observed for both large and small storms during solar cycle minimum, as discussed by Hernandez andRoble [1976aRoble [ , b, 1979a Before we attempt to discuss the physical processes that give rise to the observed behavior of the February 21, 1979, and April 25, 1979, storms, an examination of the measurements is necessary Abreu et al [1982]. calculated the effects of aerosol scattering of night sky emissions from all directions into the field of view of the instrument for the case when aerosol scattering is not negligible and large emission rate differentials occur between separate regions of the sky.…”