In this work we numerically investigated the ionospheric responses to the non-migrating atmospheric tide. The diurnal eastward wavenumber-3 (DE3) tidal mode was considered as the low boundary perturbation in the simulation based on the Global Coupled Ionosphere-Thermosphere-Electrodynamics Model, developed by Institute of Geology and Geophysics, Chinese Academy of Sciences (GCITEM-IGGCAS). We then obtained the longitudinal wavenumber-4 (WN4) structure in the ionosphere by running GCITEM-IGGCAS with several devised control conditions. The numerical simulation reveals the coupling processes with which the atmospheric tide DE3 excites the ionospheric WN4 structure. It is found that the direct wave produce the WN4 structure only in neutral parameters (e.g., the mass density). It is noticeable that the phase speed of the mass density WN4 pattern is very large (twice as that of the DE3 tide) at night and small (near to zero) in day time. This is reattributed to the nonlinear interaction between the upward propagated DE3 mode and the local migrating diurnal tide. Our results also show that the DE3 modulated electric field produces the WN4 structure in both the plasma and neutral parameters (e.g., the electron density and mass density). As expected, the latitudinal distribution of this WN4 structure is aligned with the geomagnetic latitude. It is concluded that both the upward propagation of the tidal wave and the electric field coupling play remarkable roles in producing the WN4 structure in thermosphere, and the electric field coupling is the main cause that produce the ionospheric F-region WN4 structure.