Solar and lunar tidal variabilities in GPS‐TEC and geomagnetic field variations: Seasonal as well as during the sudden stratospheric warming of 2010

The Global Positioning System (GPS) deduced total electron content (TEC) data at 15°N (geomagnetic), which is the northern crest region of equatorial ionization anomaly, are used to study solar and lunar tidal variabilities during the years 2008 and 2009 and also during the 2009–2010 winter, when a major sudden stratospheric warming (SSW) event has occurred. The diurnal and semidiurnal tidal amplitudes show semiannual variation with maximum amplitudes during February–March and September–November, whereas terdiurnal tide is larger during April–September. They show significant longitudinal variability with larger (smaller) amplitudes over 250°E–150°E (200°E–250°E). Lunar semidiurnal tidal amplitudes show sporadic enhancements during northern winter months and negligible amplitudes during northern summer months. They also show notable longitudinal variabilities. The solar migrating tides DW1 and SW2 show semiannual variation with larger amplitudes during spring equinox months, whereas TW3 maximizes during northern summer. DW2 shows larger amplitudes during summer months. During the SSW, except TW3, the migrating tides DW1 and SW2 show considerable enhancements. Among solar nonmigrating tides, SW1, TW2, and DS0 show larger enhancements. Solar tides in TEC and equatorial electrojet strength over Tirunelveli vary with the time scale of 60 days during October 2009–March 2010 similar to ozone mass mixing ratio at 10 hPa, and this confirms the vital role of ozone in tidal variabilities in ionospheric parameters. Lunar tidal amplitudes in changes in horizontal component of geomagnetic field (ΔH) are larger over Tirunelveli, a station near dip equator. Solar semidiurnal tides in ΔH have larger amplitudes than lunar tides over polar stations, Mawson and Godhavn. Plain Language Summary In this paper, the variations of solar and lunar tides in a few ionospheric parameters during the years 2008 and 2009 and during a disturbed winter are presented. We found that the migrating tides show semiannual variation, where as a nonmigrating diurnal tide DW2 shows maximum during summer. This explains the additional summer maximum observed in the seasonal variation of mesospheric tides over low‐latitude stations. Besides, the semidiurnal tidal variation shows clearly 60 day variability as shown by the stratospheric ozone. This suggests the dominant role of stratospheric ozone in the variations of upper atmospheric tides. Key Points Migrating (DW1 and SW2) and nonmigrating (SW1 and D