Ionosphere F2-region under the influence of the evolutional atmospheric gravity waves in horizontal shear flow

Abstract

The ambipolar diffusion equation for the height distribution of electron density in the ionospheric F2-layer is solved in the presence of neutral horizontal shear flow. By using this nonstationary solution the reaction of the F2-region electron density on the evolution of atmospheric acoustic–gravity waves (AGW) is investigated. The evolution of the AGW and the corresponding behaviour of the height distribution of the F2-region electron density are described by the characteristic time, t a, of transient development of shear waves in the horizontal shear flow. For long times t > t a, the gravity wave frequency tends to the isothermal Brunt–Väisälä frequency, which appears in the F2-layer as wavelike behaviour of h m F2 and N m F2 with periods close to 16–20 min, when the scale height of the neutral gas is H = 60 km. The shear wave, which is due to the presence of horizontal shear flow, gives sufficient changes of the height profile of electron density for times of t ⩽ t a.