In this study, the mechanisms of interhemispheric asymmetry of the equatorial ionization anomaly (EIA) in June solstice at solar minimum were investigated through a series of simulations using the Thermosphere Ionosphere Electrodynamics General Circulation Model. Our results indicate that the transequatorial neutral wind is the main cause of the interhemispheric asymmetry. The transequatorial wind transports plasma from the summer hemisphere to winter hemisphere, leading to an enhancement in the winter EIA crest. Meanwhile, the ion production and loss are also important factors in producing the EIA asymmetry through photochemical processes. The longitudinal variations of the EIA interhemispheric asymmetry are also explored through imposing each term of ion continuity equation longitudinally independent. Our term analysis results suggest that the neutral wind variation dominates the longitudinal patterns of the interhemispheric asymmetry, while the E × B drift and photochemical process contribute less.

It is commonly believed that solar eclipses have a great impact on the ionosphere‐thermosphere (I‐T) system within the eclipse shadow, but little attention has been paid to the global response to these events. In this study, we investigate the global upper atmospheric responses to the recent Great American Solar Eclipse that occurred on 21 August 2017 using a high‐resolution coupled ionosphere‐thermosphere‐electrodynamics model. The simulation results show that the ionosphere and thermosphere response to the eclipse is not just local but global. Large‐scale traveling atmospheric disturbances (TADs), seen in the thermospheric temperature and winds, were triggered from the eclipse region and propagated in a southeast direction when the eclipse ended. A large total electron content (TEC) enhancement occurred over South America after the eclipse was over. The TEC enhancement was primarily the result of transport by the thermospheric wind perturbations associated with the eclipse‐induced TADs. The perturbations of TEC, neutral temperature, and winds exhibited asymmetric distributions with respect to the totality path during the solar eclipse. Furthermore, ionospheric electrodynamic processes also play an important role in the global responses of the I‐T system to the solar eclipse. Unlike the case of large‐scale TADs propagating from the eclipse region to other locations in the globe, the ionospheric electric fields and plasma drifts began to show significant perturbations even during the local pre‐eclipse period when local wind and temperature had not been perturbed. This is related to the instantaneous global response of the ionospheric current system to changes in the ionospheric conductivity and winds in the eclipse region.

The understanding of the Earth's space environment has grown exponentially over the centuries since the step into space age (Jacchia, 1959). The so-called space weather, which describes the "weather" changes in solar-terrestrial connections, has shown broad influences in civilian life, commerce, and national security, including communication, navigation, electric grids and satellite operations (