The ionosphere-thermosphere (I-T) system is controlled by complicated chemical and physical processes that vary with external forcing and internal dynamics. This variability becomes much stronger during storms, when the interaction between the solar wind and geospace produces significant energy and momentum inputs to the system, changing high-latitude convection, composition, winds and temperature. These storm-time, high-latitude perturbations are then transmitted to middle and low latitudes, through non-linear dynamics and electrodynamics, such as penetration electric fields, disturbance dynamo, and traveling atmosphere/ionosphere disturbances (TADs/TIDs), changing global neutral and plasma densities and producing structures of different spatial and temporal scales. Recent advances in coupled geospace models and space-borne and ground-based observations provide new opportunity to explore the fundamental coupling physics in the I-T system during geomagnetically active periods and its feedback effects on magnetospheric dynamics. This session welcomes presentations of both observations and modeling on the dynamic changes of the I-T system during storms.