Is DE2 the Source of the Ionospheric Wave Number 3 Longitudinal Structure?

This study examines the connection of the wave number 3 (wave-3) longitudinal structure in the ionospheric plasma density with diurnal eastward propagating zonal wave number 2 tide (DE2) by examining the annual and diurnal variations of the wave-3 structures in the plasma density and vertical E × B drift. For this purpose, we have utilized the mean plasma density and vertical ion velocity derived from the first Republic of China satellite data during 1999-2004 under Kp < 4 condition. Good correlation between the wave-3 longitudinal structures in the plasma density and vertical E × B drift indicates that the vertical E × B drift (or E-region dynamo electric field) is responsible for the creation of the wave-3 plasma density structure. The annual variation of the amplitude of the ionospheric wave-3 structure in the plasma density and vertical E × B drift shows two peaks near December and May, which is consistent with the annual variation of the DE2 amplitude. However, the diurnal variation of the ionospheric wave-3 structure does not show the eastward phase shift of 120°/24 LT that is predicted by DE2. The amplitude of the ionospheric wave-3 structure is greater than might be predicted by the comparison of the amplitude of the DE3 and DE2 winds. Another mechanism in addition to DE2 is necessary in order to explain the formation of the ionospheric wave-3 longitudinal structure.