Drivers of F-Region Ionosphere Tidal Variability Caused by the Madden Julian Oscillation: Separating E-Region Dynamo and Field-Aligned Wind Effects

The Madden–Julian Oscillation (MJO), a recurring intraseasonal (30–96 days) disturbance in the troposphere, strongly influences the E-region and F-region ionosphere through its modulation of atmospheric tides. Among these, the diurnal eastward wave number 3 (DE3) tide, driven by MJO-modulated latent heating, carries MJO signals upward into the E-region. However, coupling into the F-region remains poorly understood due to the lack of direct thermospheric neutral wind observations. To address this, we investigate MJO propagation from the E-region to the F-region using simulations from the Thermosphere Ionosphere Electrodynamics General Circulation Model (TIE-GCM) nudged with outputs from the Specified Dynamics Whole Atmosphere Community Climate Model with thermosphere ionosphere Extension (SD-WACCM-X). The results show that DE3 amplitudes in F-region electron density (∼300 km, 15°N) vary by about ∼ 20%. The simultaneous response of E-region zonal winds, F-region vertical drifts, and electron density highlights the role of the E-region dynamo. Controlled simulations reveal that ∼ 73% of DE3 MJO perturbations are transported by vertical drifts, with the remainder by neutral winds. The semidiurnal eastward wave number 2 (SE2) tide contributes about 65% of its variability transmitted via field-aligned neutral winds. While SE2 plays a secondary role (∼10%, half of DE3), DE3 dominates the tidal variability, emphasizing the E-region dynamo's control over the ionospheric response. The MJO further modulates zonal mean F-region electron density by 4%–5%, primarily through semidiurnal westward (SW2) migrating tides. These results highlight how MJO–tide interactions shape ionospheric variability, with potential impacts on satellite drag, navigation, and communication systems.