摘要：Temporal and longitudinal variations of the pre-reversal enhancement (PRE) in the equatorial F region vertical plasma drift are examined based on idealized simulations by the thermosphere-ionosphere-electrodynamics general circulation model performed under geomagnetically quiet (Kp = 1) and high solar-flux (F10.7 = 200) conditions. The model takes into account forcing by large-scale waves from the middle and lower atmosphere, which leads to day-to-day variations of PRE. Simulations are performed under different wave forcing in order to separate contributions of various types of waves. It is shown that the simulated day-to-day variability of the PRE intensity is predominantly due to forcing by waves with periods less than 2 days, that is, tides and their modulation. Planetary-wave forcing (periods of 2–20 days) makes contributions to periodic oscillations in the PRE intensity. Especially, the westward-propagating quasi-6-day wave (Q6DW) with zonal wavenumber 1 is found to be an important source of ∼6-day oscillations of PRE. Not only the Q6DW from below but also the Q6DW generated within the thermosphere, as well as the secondary waves due to the nonlinear interaction between the Q6DW and migrating tides, is at play. The zonal wavenumber 1 nature of the ∼6-day oscillations could contribute to longitudinal differences in the appearance of equatorial spread F and plasma bubbles, which are strongly controlled by PRE.
