Attribution of ionospheric vertical plasma drift perturbations to large-scale waves and the dependence on solar activity

SW1 can cause large vertical drifts around dawn, while QSPW1 does not have any direct impact on the vertical drift. Wind components of both SW2 and SW1 become large at middle to high latitudes in the E-region, and kernel functions obtained from numerical experiments reveal that they can significantly affect the equatorial ion drift, likely through modulating the E-region wind dynamo. The most evident changes of total ionospheric vertical drift when solar activity is increased are seen around dawn and dusk, reflecting the more dominant role of large F-region Pedersen conductivity and of the F-region dynamo under high solar activity.

Therefore, the lower atmosphere driving of the ionospheric variability is more evident under solar minimum conditions, not only because variability is more identifiable in a quieter background but also because the E-region wind dynamo is more significant. These numerical experiments also demonstrate that the amplitudes, phases, and latitudinal and vertical structures of large-scale waves are important in quantifying the ionospheric responses.