Forcing from Lower-Thermosphere and Ionospheric Dynamics during Extreme Events

The gravity waves (with a spatial scale of 10 to 1000s km and temporal scale of minutes to hours) has been considered as a potential seeding mechanism for the development of small-scale ionospheric irregularities. The GWs (mainly generated in the tropospheric convective regions) propagate upward at slant angles to the height of ionosphere and produce clear periodic structures with horizontal scale size of a few hundred kilometers (medium-scale traveling ionospheric disturbances (MSTIDs)), and eventually initiate the Rayleigh-Taylor instability (RTI) that result ionospheric irregularities. Recent case studies show that the GWs is the localized events and may produce different ionospheric density perturbations at different longitudes, that include triggering the poleward propagating MSTIDs at different longitudes with different structures and amplitudes. In this paper, using coordinated multi-instrument observations that include density perturbations (using GPS, radars, ionosondes, and satellites measurements) and GWs amplitude (from SABER temperature profiles measurements onboard TIMED satellite), we investigate the role the troposphere-lower thermosphere-ionosphere coupling to the ionospheric density perturbation, especially during major sudden stratospheric warming events. Understanding the physical processes that control the longitudinal variability of density perturbations during major SSW events is very relevant for the effort of improving the orbital tracking, radio communications, and navigation systems that are very important for the operation of ships and aircraft.