Ionospheric Interhemispheric Asymmetry Induced by Planetary Wave Under Solar Minimum Condition

Abstract

AbstractThe westward quasi‐6‐day planetary wave with zonal wave number 1 (Q6DW) is important in the Earth's atmospheric coupling. The International Global Navigation Satellite System Service total electron content (TEC) maps show that the Q6DW‐related ionospheric perturbations exhibit clear interhemispheric asymmetry, which do not always agree with the interhemispheric asymmetry feature of the background TEC. The National Center for Atmospheric Research Thermosphere‐Ionosphere‐Mesosphere Electrodynamic General Circulation Model is then used to investigate the reasons for planetary wave‐induced interhemispheric asymmetry by imposing Q6DW forcing at the model lower boundary at vernal equinox under solar minimum condition. The interhemispheric asymmetry features of the ionospheric responses to Q6DW are well captured by our model simulations. For example, the southern branch of the Q6DW perturbation in F region is ~26% larger than that in the Northern Hemisphere at 30°E, while the background Model TEC is~4.7% stronger in the Northern Hemisphere. We found that the vertical plasma transportation induced by Q6DW perturbations in the neutral wind fields in F region show the same asymmetric features with TEC, which leads to corresponding ionospheric perturbations by changing the local recombination effect. Our further simulations show that the vertical plasma drifts induced by Q6DW through E × B process can also cause interhemispheric asymmetry in Model TEC. It is also found that the zonal component of Q6DW perturbations contributes more to the asymmetry than the meridional component through both neutral wind direct transportation effects and E region wind dynamo effects. Moreover, the ionospheric asymmetry of the Q6DW‐related oscillations also exhibit clear longitudinal variabilities.