Multiple observational studies have demonstrated large ionospheric variations during the daytime associated with sudden stratospheric warming (SSW) events, but only limited evidence of ionospheric disturbances during the nighttime has been reported up to now. We focus on the American longitudinal sector with its extensive observational network of Global Navigation Satellite System receivers, four Digisondes located at low and middle latitudes, and the 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 total electron content that reaches a factor of 2–5 as compared to the background level and is observed between local midnight and local sunrise (6–12 UT). This decrease is observed for several consecutive days in the range of latitudes from ~55°S to ~45°N. 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. These results demonstrate that SSW events cause changes in the nighttime ionosphere that are even larger than in the daytime ionosphere. We discuss variations in electric field and F-region dynamics as possible drivers of this behavior and suggest that thermospheric winds play a much larger role than previously thought.
All Science Journal Classification (ASJC) codes
- Space and Planetary Science