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

Abstract

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.

Identification of the mechanisms responsible for anomalies in the tropical lower thermosphere/ionosphere caused by the January 2009 sudden stratospheric warming

“…(1) an evening time EIA enhancement in TEC; (2) nighttime negative disturbances in TEC. The second finding confirms the recently proposed relationship between the SSW event and nighttime decrease in TEC (Goncharenko et al, 2018) for another SSW event in 2013. So, given that the EAGLE model results adequately reproduce most of the observed features in TEC diurnal variations, we can use them to investigate the formation mechanism of such TEC disturbances.…”

“…The prolonged continuous minimum of solar and geomagnetic activity over 2007-2009 allows a careful examination of relationships between processes in the middle and upper atmosphere, as for this period, solar and magnetospheric sources in upper atmosphere variability were minimized (Goncharenko et al, 2010a). January 2009 presents a unique major SSW event that was very strong and long-lasting (Labitzke & Kunze, 2009).…”

“…For example, during the January 2009 SSW event, observed morning-noon enhancements and afternoon decreases in the electron density at low latitudes (Chau et al, 2012) are much less pronounced or absent in model results (Goncharenko et al, 2010b, Jin et al, 2012Klimenko et al, 2015;Pedatella et al, 2016). Several studies conclude that the primary mechanism responsible for total electron content (TEC) disturbances at low latitudes during the 2009 SSW event is a perturbation of the zonal electric field (the vertical E Â B plasma drift) (Goncharenko et al, 2010a;Jin et al, 2012;Pedatella et al, 2012;Klimenko et al, 2015). Recently, several authors exploited different models and simulation techniques (e.g., assimilation of data or dynamical nudging) to reproduce the observed equatorial electromagnetic drift disturbances during the 2009 SSW event (Fuller-Rowell et al, 2011a;Jin et al, 2012;Pedatella et al, 2016).…”

“…Another important aspect is the identification of physical mechanisms explaining the low-latitude TEC anomalous variability connected to lower atmospheric processes. After the first model attempts to reproduce the strong ionospheric SSW signature (Goncharenko et al, 2010b), many numerical experiments with varying degrees of success in reproducing low-latitude TEC disturbances in the American longitudinal sector were presented (Jin et al, 2012;Klimenko et al, 2015;Pedatella et al, 2016Pedatella et al, , 2018. Klimenko et al (2015) demonstrated that only the inclusion of additional upward and downward electromagnetic plasma drift velocities to the GSM TIP model allowed the observed pre-noon positive and daytime negative TEC disturbances in the equatorial ionization anomaly region associated with the 2009 SSW event to be reproduced.…”

“…Despite recent progress in model development, disagreement between the modeled and observed upper atmosphere responses to SSW events still exists due to difficulties in the treatment of non-linear interactions between stationary planetary waves, atmospheric tides, and gravity waves (Pedatella et al, 2016). For example, during the January 2009 SSW event, observed morning-noon enhancements and afternoon decreases in the electron density at low latitudes (Chau et al, 2012) are much less pronounced or absent in model results (Goncharenko et al, 2010b, Jin et al, 2012Klimenko et al, 2015;Pedatella et al, 2016). Several studies conclude that the primary mechanism responsible for total electron content (TEC) disturbances at low latitudes during the 2009 SSW event is a perturbation of the zonal electric field (the vertical E Â B plasma drift) (Goncharenko et al, 2010a;Jin et al, 2012;Pedatella et al, 2012;Klimenko et al, 2015).…”