Atmospheric Gravity Waves Generation by Solar Terminator According to “Atmosphere Explorer-E” Satellite Data

Abstract

The upperatmospheric neutral and ionized components dynamical response on a moving solar terminator is investigated employing the direct satellite measurements. The observations from “Atmosphere Explorer-E” are analyzed for the period of the satellite being in a circular near-equatorial orbit with the inclination <i>i</i>=19.7° and height 250-300 km. It came to light that the terminator generates the large-scale atmospheric gravity waves (AGW) and traveling ionospheric disturbances (TID) with the following parameters: the horizontal wavelength of about 1200-1600 km; the calculated period of about 50 min; the wavetrain duration of four-to-six periods; the relative AGW amplitude of several percent; the relative TID amplitude at sunrise terminator of about several percent, rising to tens percent at sunset terminator. The primary ion O⁺ density oscillates in opposite phase, while that of molecular ions NO⁺ and O₂⁺ does in phase, with the density oscillations of the main neutral components N₂ and O. The experimental findings are interpreted in terms of the theory of AGW propagation in a multi-component gas medium. It is shown that the amplitude and phase distinctions in the oscillations of atmospheric components (including the main ionic component O⁺) are caused by the differences in their vertical distributions above the turbo-pause. The mechanism of AGW and TID generation at the F-region heights due to electron gas pressure gradient is suggested.