Correlation between ionospheric longitudinal harmonic components and upper atmospheric tides

Abstract

There is strong correlation among the ionospheric longitudinal structures of wavenumber-3 (WN3), wavenumber-4 (WN4), and eastward-propagating diurnal tides with zonal wave numbers s = 2 and 3 (DE2 and DE3) in the upper atmosphere. The total electron content derived from the Global Ionospheric Maps of the Jet Propulsion Laboratory is used to deduce the latitudinally total electron content (ITEC) in the low-latitude ionosphere, and TIDE/TIMED observations are employed to obtain zonal and meridian winds of the mesopause and lower thermosphere. Through Fourier transformation, various ionospheric longitudinal harmonic components and tidal patterns are derived from the ionospheric and upper-atmospheric observations, and we compare the annual/inter-annual variations in ionospheric harmonic components WN3 and WN4 with those in atmospheric tides (DE2 and DE3). It is found that the annual and inter-annual variations in WN3 and WN4 are consistent with those in DE2 and DE3 zonal wind components respectively, while they are inconsistent with those in the meridian components. We then decompose the harmonic components into “tidal patterns”, finding that the “DE2” and “DE3” patterns are the main parts of WN3 and WN4 respectively. Their annual and inter-annual variations are similar to those of atmospheric tidal patterns (DE2 and DE3). Complex correlation results show that correlation between the ionospheric “DE2” in WN3 and the atmospheric tidal DE2 zonal wind component is quite strong in the Northern Hemisphere, while that between the ionospheric “DE3” in WN4 and the atmospheric tidal DE3 zonal wind component is much stronger at low latitudes. At the same time, the contribution of the meridian wind component is very weak. Above all, the atmospheric tidal DE2 and DE3 patterns are important factors of the ionospheric WN3 and WN4 structures.