Long term investigation of the lunar tide in the equatorial electrojet during stratospheric sudden warmings The ionosphere which is strongly influenced by the Sun is known to be also affected by meteorological processes. These processes despite having their origin in the troposphere and stratosphere interact with the upper atmosphere. Such an interaction between atmospheric layers is known as vertical coupling. During geomagnetically quiet times when near Earth space is not under the influence of solar storms these processes become important drivers for ionospheric variability. Studying the link between these processes in the lower atmosphere and the ionospheric variability is important for our understanding of fundamental mechanisms in ionospheric and meteorological research. A prominent example of vertical coupling between the stratosphere and the ionosphere are the so called stratospheric sudden warming (SSW) events that occur usually during northern winters and result in an increase in the polar stratospheric temperature and a reversal of the circumpolar winds. While the phenomenon of SSW is confined to the northern polar…