Stable and unstable plasma perturbations in the ionospheric F region, caused by spatial packet of atmospheric gravity waves

A new model is developed to describe the response of the unstable near-equatorial F region plasma to the spatial packet of atmospheric gravity waves (AGWs) of the lithospheric origin. Presence of both propagating and non-propagating (upward) modes in the spectrum of exited AGW packet is accounted for. It is shown that peculiarities of spectral and spatial distributions of relative perturbation of ion concentration in the ionosphere are determined by spectrum peculiarities of both AGW and increment of plasma instability. It is shown, in particular, that both periodical structures with spatial period of order of 500–800 km (for AGW periods of order of 25–40 min) and localized structures with characteristic dimension of the order of 1000–2000 km are excited in plasma, and localized plasma structures are shifted to the west over the distance of a few thousand kilometers relatively to the maximum of the neutral atmosphere response in the presence of eastward wind.