The Role of the Polar Vortex in Sun-Earth Coupling

Abstract:

In the polar regions, the wintertime polar vortices play a critical role in both "bottom-up" atmospheric coupling via its modulation of planetary and gravity waves as well as "top-down" coupling via the transport of nitrogen oxides created by energetic particle precipitation. This talk will present the current state of understanding regarding the role of the polar vortex in coupling different atmospheric layers via both “bottom-up” and “top-down” processes. In particular, for “bottom-up” coupling, the polar vortices act to vertically couple the atmosphere from the troposphere to geospace by shaping the background wind field through which atmospheric waves propagate. For a variety of reasons, the geographic distribution of gravity wave (GW) activity depends on the strength and shape of the polar vortex. Vortex modulation of atmospheric GWs then impacts the abundance of traveling ionospheric disturbances. For “top-down” coupling, energetic particle precipitation (EPP) generates nitrogen oxides (NOx=N+NO+NO2) in the mesosphere-lower thermosphere polar regions. In the wintertime, the polar vortices play a key role in downward coupling the thermosphere to the stratosphere by focusing the descent of EPP-NOx within their cores. State-of-the-art global climate models severely underestimate EPP-NOx transport during disturbed Arctic winters. Recent advances in both “bottom-up” and “top-down” coupling will be presented. Outstanding questions and future directions will be discussed.