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An earthquake is a seismic event resulting from a sudden release of energy in the lithosphere, which produces waves that can propagate through the atmosphere into the ionosphere, causing ionospheric disturbances, and excites an additional electric field in the lower ionosphere. Two large-scale traveling ionospheric disturbances (LSTIDs) at daytime Turkey longitudes were found, with phase speeds of 534 and 305 m/s, respectively, after the second strong earthquake at 10:24 UT on 6 February 2023. During strong earthquakes, the equatorial ionospheric currents including the E-region equatorial electrojet (EEJ) and F-region ionospheric radial current (IRC) might be perturbed. At the Tatuoca station in Brazil, we observed a stronger-than-usual horizontal magnetic field associated with the EEJ, with a magnitude of ~100 nT. EEJ perturbations are mainly controlled by neutral winds, especially zonal winds. In the equatorial F-region, a wave perturbation of the IRC was caused by a balance of the electric field generated by the zonal winds at ~15° MLat, the F-region local winds driven by atmospheric resonance, and the additional polarization electric field. Our findings better the understanding of the complex interplay between seismic events and ionospheric current disturbances. 

Abstract Previous studies have shown that solar flares can significantly affect Earth's ionosphere and induce ion upflow with a magnitude of ∼110 m/s in the topside ionosphere (∼570 km) at Millstone Hill (42.61°N, 71.48°W). We use simulations from the Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model (TIEGCM) and observations from Incoherent Scatter Radar (ISR) at Millstone Hill to reveal the mechanism of ionospheric ion upflow near the X9.3 flare peak (07:16 LT) on 6 September 2017. The ISR observed ionospheric upflow was captured by the TIEGCM in both magnitude and morphology. The term analysis of the F‐region ion continuity equation during the solar flare shows that the ambipolar diffusion enhancement is the main driver for the upflow in the topside ionosphere, while ion drifts caused by electric fields and neutral winds play a secondary role. Further decomposition of the ambipolar diffusive velocity illustrates that flare‐induced changes in the vertical plasma density gradient is responsible for ion upflow. The changes in the vertical plasma density gradient are mainly due to solar extreme ultraviolet (EUV, 15.5–79.8 nm) induced electron density and temperature enhancements at the F₂‐region ionosphere with a minor and indirectly contribution from X‐ray (0–15.5 nm) and ultraviolet (UV, 79.8–102.7 nm).