Figure 4

The mean normalized power of the quasi-16-day periodicities in EEJ strength and TEC. The power spectra as shown in Figure 3 are averaged between 11.5- and 20-day periods and for the whole day. The letters ‘m’ and ‘M’ represent ‘minor’ and ‘major’ SSW events, respectively, that occurred in the given year. The dashed curve shows the high-latitude stratospheric temperature anomaly (∆T) on the peak of the SSW-related warming that represents the lower atmospheric behavior. One can note that the amplitudes have three peaks during the three strong major SSW events in the years 2006, 2009, and 2013 and three minima during the minor events in 2005, 2011, and 2012. It can be noted that there is a clear and systematic correspondence between the quasi-16-day amplitudes and the polar stratospheric temperature anomaly. The average SSN values are also shown with its axis at the right. It may also be noted that the relatively higher solar activity year 2013 showed a strong coupling due to increased lower atmospheric activity during strong SSW event.