Longitudinal variability of thermospheric temperatures from WINDII O (~1S) dayglow

摘要

A topic of great current interest in atmospheric dynamics is the developing recognition of the influence of the diurnal eastward-propagating non-migrating tide of wave number 3 (DE3) on the thermosphere. Longitudinal variations of the equatorial F region ionospheric electron density show a zonal wave number 4 (wave-4, WN4) pattern, expected for satellite observations at a fixed local time with respect to a rotating Earth. WINDII observations of airglow O (~1S) volume emission rate (VER), excited by photoelectron impact on atomic oxygen at 250km have previously been interpreted as neutral density observations; they have shown the wave 4 to be a common density perturbation in the equatorial thermosphere. The analysis has been extended further by examining thermospheric neutral temperatures from September 1992 to April 1993 at 245km height derived from the vertical gradient of the observed daytime O(~1S)VERs at 235-255km yielding the atomic oxygen density scale heights centered at this altitude. The thermospheric temperatures show a distinct and persistent wave-4 signature at 20S-40S with a pronounced increase during March equinox.