North American SuperDARN Observations of Medium-Scale Traveling Ionospheric Disturbances During January 2016

Medium-Scale Traveling Ionospheric Disturbances (MSTIDs) are quasi-periodic variations of F-region ionospheric densities that are most often associated with atmospheric gravity waves (GWs) generated in the lower neutral atmosphere. MSTIDs can affect the accuracy of GPS signals and the range of high frequency (HF, 3-30 MHz) terrestrial communications and thus have important societal impacts. The ionospheric variations caused by MSTIDs can focus and defocus HF radio signals, propagating through the ionosphere, thereby causing changes in the range at which these radio signals are refracted back to Earth. Using this principle, high frequency radars such as those in the Super Dual Auroral Radar Network (SuperDARN) can be used to observe MSTIDs. The SuperDARN MSTID Multiple Signal Classification (MUSIC) Algorithm can be used to determine the period, wavelength, speed, and direction of propagation of the observed MSTIDs. We present SuperDARN observations over the North American continent for the period of 11-16 January 2016. This period is known to be important in terms of the polar vortex generating GWs that seed MSTID activity through multi-step vertical coupling processes. A period of low MSTID activity is observed from 11-13 January followed by a period of elevated MSTID activity from 14-16 January. We attribute low and high MSTID levels to fluctuating gravity wave activities modulated by the polar vortex.