Deep Ionospheric Hole Created by Sudden Stratospheric Warming in the Nighttime Ionosphere

Abstract:

Multiple observational studies have demonstrated large ionospheric variations associated with sudden stratospheric warming (SSW) events during the daytime, but only limited evidence of ionospheric disturbances during the night-time was reported up to now. We focus on the American longitudinal sector with its extensive observational network and utilize observations by GPS receivers, three digisondes located at low and middle latitudes, and Arecibo and Millstone Hill incoherent scatter radars. The study focuses on a major SSW event of January 2013 to investigate large-scale disturbances in the nighttime ionosphere. We report a deep decrease in TEC that reaches a factor of 2-6 as compared to the background level and is observed between the local midnight and local sunrise (6-12UT). This decrease is observed for several consecutive days in the range of latitudes from ~55^oS to ~45^oN. It is accompanied by a strong downward plasma motion and a significant decrease in ion temperature, as observed by both Arecibo and Millstone Hill radars. We discuss variations in electric field and F-region dynamics as possible drivers of this behavior.