The Role of the Polar Vortex in Atmosphere-Ionosphere Coupling

In the polar regions, the wintertime polar vortices play a critical role in "bottom-up" atmosphere-ionosphere coupling via the generation and modulation of atmospheric gravity waves (GWs) and via interactions with planetary waves (PWs). This talk will first present a tutorial on the polar vortex: why it forms, where and when it exists, and variability in vortex strength sub-seasonally (within each winter), inter-annually (from winter-to-winter), and inter-hemispherically (in the Arctic and Antarctic). I will then present the current state of understanding regarding the role of the polar vortex in coupling different atmospheric layers via “bottom-up” processes. In the last decade it has become widely accepted that PW-driven sudden stratospheric warmings (SSWs) cause variability in the thermosphere-ionosphere system. Recent results demonstrate that strong polar vortex events result in variability of the opposite sign than is observed during SSWs. In addition, the geographic distribution of smaller-scale GWs depends on the strength and shape of the polar vortex. The polar vortices act to vertically couple the atmosphere from the troposphere to geospace by changing the background wind field through which GWs propagate. Recent work demonstrates that localized jet cores around the polar vortex also act as a middle atmosphere source for GWs. Vortex modulation and generation of atmospheric GWs then impact the abundance of traveling ionospheric disturbances that may impact Ham radio communications.