Effects of acoustic–gravity waves on the total electron content of the Martian ionosphere

ABSTRACT The total electron content (TEC) is a key diagnostic for the structure and variability of the ionosphere. Acoustic–gravity waves (AGWs), originating from the lower atmosphere of Mars, can propagate into the thermosphere–ionosphere system and perturb the ionospheric plasma, yet their impact on TEC remains unexplored. In this study, we used a linear coupled wave model to investigate TEC variations induced by AGWs. Our results indicate that TEC distributions are strongly regulated by the magnetic field topology and ionospheric electrodynamics. Under a horizontal magnetic field, the TEC distribution exhibits pronounced horizontal anisotropy. It remains symmetric when only neutral wind drag is included but becomes laterally asymmetric once full electrodynamic effects are considered. In contrast, TEC remains horizontally isotropic under a vertical magnetic field regardless of electrodynamic effects. The TEC variations depend on the wave mode. High-frequency acoustic waves induce small TEC variations, with maxima of ∼2 per cent. Low-frequency gravity waves cause larger TEC variations, from a few per cent to several tens of per cent. For a horizontal magnetic field, the maximum TEC ratios for the acoustic and gravity branches increase from ∼1 per cent and 6 per cent to 2 per cent and 26.7 per cent when electrodynamic effects are included, whereas under a vertical magnetic field the corresponding values remain much smaller (∼0.02 per cent–0.47 per cent and 2.85 per cent–3.2 per cent). This study provides the first quantitative investigation of the effects of AGWs on TEC in the Martian ionosphere, revealing multilayer coupling processes and suggesting that TEC measurements can infer wave properties and local magnetic field topology.