Wavenumber‐4 Longitudinal Structure in ICON‐MIGHTI Thermospheric Meridional Wind

Abstract

AbstractThe present study investigates wavenumber‐4 (wave‐4) structure in the longitude variation of zonal and meridional winds observed by the Michelson Interferometer for Global High‐resolution Thermospheric Imaging (MIGHTI) instrument onboard the Ionospheric Connection Explorer (ICON) satellite. The amplitude of the wave‐4 pattern in meridional wind displays semi‐annual variation with equinoctial maxima whereas its seasonal variation in zonal wind shows maxima during August–October at the equatorial and low latitudes. The wave‐4 longitude variation maximizes at lower thermospheric heights (below 130 km) in zonal and meridional winds. It is considered primarily driven by the non‐migrating eastward propagating diurnal tide with zonal wavenumber‐3 (DE3) in the zonal wind. However, the amplitude of DE3 tide in the meridional wind does not show any enhancement during September–October. The seasonal variations of the wave‐4 amplitude and the DE3 tide are not similar in the zonal and meridional winds. The migrating ter‐diurnal tide (TW3) exhibits significant amplitudes during March–April and September–November in the meridional wind. In addition, the latitude variation of non‐migrating TE1 tide shows maximum amplitude during September–October. These results suggest that the non‐linear interaction between the TW3 and TE1 tides can serve as a potential source for the wave‐4 longitude variation in the meridional wind at lower thermospheric altitudes.