New Insights on Connections between the Middle Atmosphere and Ionosphere: Ionospheric Changes during Sudden Stratospheric Warmings of 2016–18

The influence of sudden stratospheric warmings (SSW) extends beyond the stratosphere into the upper thermosphere and ionosphere, where it produces persistent multi-day variations in electron density that are comparable to variations caused by geomagnetic storms. Rising awareness by the geospace research community about the significance of such processes, in conjunction with increasing availability of GNSS TEC data and the high occurrence rate of sudden stratospheric warmings from 2016 to 2018, provide motivation and enable in-depth studies of the fundamental physical processes that are responsible for SSW-induced ionospheric variations. To develop a more robust picture of the ionospheric response to SSWs, we analyze ionospheric variations for 5 months (November – March) in each of the past three Arctic winters. In particular, we focus on the low-latitude and equatorial ionosphere in several distinct longitudinal sectors: African (40E), Asian (120E), and American (75W). Our analysis reveals some common behavior in the equatorial ionization anomaly (EIA), in particular a 12-hr variation related to electric field effects. We report ~50% changes in the strength of the northern crest of the EIA and 50-90% changes in the southern EIA crest. In contrast to previously studied SSW cases, we find that SSWs cause largest ionospheric impacts in the afternoon sector. We also report that the minor SSW of 2016 is linked to stronger ionospheric variations than the major SSW of 2018.