![]() Owing to larger topographic and land-sea contrasts, the PWs in the Northern Hemisphere (NH) have larger amplitudes than in the Southern Hemisphere (SH) (e.g., Waugh 2017), which results in the NH SPV being weaker and more prone to distortion than the SH SPV (e.g., Waugh and Randel 1999). Air converges and descends at high-latitudes resulting in warming of the polar stratosphere. These planetary waves (PWs) can propagate vertically and break in the polar stratosphere resulting in the deposition of westward momentum (McIntyre and Palmer 1983), which decelerates the eastward winds of the SPV. ![]() The SPV experiences large inter-annual variability due to interaction with upward propagating planetary-scale waves that are forced from the troposphere (e.g., Charney and Drazin 1961 Matsuno 1971). 2018) but the strength of the mesospheric polar vortex is not considered in this study. The polar vortex extends well into the mesosphere (Harvey et al. The stratospheric polar vortex (SPV) is characterized by a band of strong eastward winds that encircle the mid- to high- latitude polar region and span from about 100 hPa to above 1 hPa in altitude. Graphical Abstractĭuring winter, the latitudinal variation in insolation causes a large-scale temperature gradient between mid-latitudes and the pole, which results in the formation of the polar vortex in the stratosphere (Baldwin et al. ![]() These results provide observational evidence that along with weak polar vortices in the Northern Hemisphere, the strong stratospheric polar vortices also have pronounced effects on the equatorial ionosphere. Our results also reveal that the response of the geomagnetic semidiurnal solar tidal variations to strong and weak polar vortex conditions is delayed by approximately 10 days while the response of geomagnetic semidiurnal lunar tidal variations do not show a time delay. When the stratospheric polar vortex is strong, geomagnetic semidiurnal solar and lunar tidal amplitudes decline on an average by ~ 15% and ~ 25%, respectively, during weak polar vortex events. During weak polar vortex events, geomagnetic semidiurnal solar and lunar tidal amplitudes show an average enhancement by ~ 25% and ~ 50%, respectively, which is consistent with the known results during sudden stratospheric warmings. ![]() We analyze the periods between December 15 and March 1 for 34 NH winters between 19 and find that the response of semidiurnal solar and lunar tides as seen in geomagnetic field depends on the strength of the stratospheric polar vortex. The impact of strong and weak stratospheric polar vortices on geomagnetic semidiurnal solar and lunar tides is investigated during Northern Hemisphere (NH) winters using ground-based magnetic field observations at the Huancayo (12.05° S, 284.67° E magnetic latitude: 0.6° S) equatorial observatory. ![]()
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