Sudden Stratospheric Warming Impacts on the Ionosphere-Thermosphere System: A Review of Recent Progress

The last decade has seen rapid progress in understanding of mechanisms coupling the upper atmosphere (thermosphere and ionosphere) with the atmospheric layers below it. These studies particularly benefited from focusing on sudden stratospheric warming events, which represent the largest known type of meteorological disturbance. As the state of the middle atmosphere rapidly changes during sudden stratospheric warmings, this change disrupts typical propagation paths of atmospheric waves that connect the lower and upper atmospheres. The modified wave spectrum drives substantial variability in the thermosphere-ionosphere. This chapter discusses recent progress in understanding upper atmosphere variability during sudden stratospheric warmings based on both observations and simulations, and outlines a number of unresolved topics.