HAO Colloquium - Tarique Siddiqui, HAO

Relationship between lunar tide of the equatorial electrojet and Sudden Stratospheric Warmings

The ionosphere, which is strongly influenced by the Sun, is also known to be affected by meteorological phenomena originating in the lower atmosphere. The lower atmospheric forcing effects on the ionosphere are particularly evident during extreme meteorological events known as sudden stratospheric warmings (SSWs). During SSWs, the polar stratosphere and ionosphere, two distant atmospheric regions, are coupled through the SSW induced modulation of atmospheric migrating and non-migrating tides. The changes in the migrating semidiurnal solar and lunar tides are the major source of ionospheric perturbations during SSWs. 

In this work, we investigate the enhancement of the lunar tides of the equatorial electrojet (EEJ) during SSWs. The EEJ is a narrow but an intense current flowing  above the dip equator during the daytime in the E-region of the ionosphere. The day-to-day variability of the EEJ can be determined from magnetic field records at geomagnetic observatories close to the dip equator. Such magnetic data are available for several decades and allows us to investigate the impact of SSW events on the EEJ and even more importantly helps in understanding the effects of SSW events on the equatorial ionosphere. An excellent long-term record of the geomagnetic field at the dip equator from 1922 onwards is available for the Huancayo observatory in Peru. These long-term observations allow us to capture the EEJ lunar tidal response to the SSWs in a statistical sense. We also examine the influence of solar flux conditions and the phases of Quasi-Biennial Oscillation (QBO) on the lunar tide and find that the QBO phases and solar flux conditions modulate the EEJ lunar tidal response during SSWs in a similar way as they modulate the winter-time Arctic polar vortex. We report here on the first evidence of modulation of the EEJ lunar tide due to QBO.


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Wednesday, April 11, 2018 - 2:00pm to 3:00pm