Do the Vertical Movements of the Peak Height of F Region Truly Represent the Vertical E × B $\mathbf{E}\times \mathbf{B}$ Plasma Drift Velocity Over the Dip Equator?

Abstract

This study examines the reasons for the difference observed between the $E\times B$ plasma drift and the drift calculated by tracing the movement of the ionospheric $F_2$ region peak, using a quasitwo-dimensional theoretical ionospheric model. Analysis shows that vertical drift causes the electron density profiles in the $F_2$ region to steepen, where photochemistry dominates, and pushes the plasma to higher altitudes. Photochemical processes result in the lower peak $\left(hm{F}_2\right)$, while the upper peak $\left(hpF\right)$ is attributed to vertical drift, which is difficult to trace due to diffusion effects. The close agreement between model-derived $\Delta hpF/\Delta t$ and Scherliess-Fejer (SF) vertical drifts confirms that the $F_2$ peak does not respond to vertical drift if it is below 300 km. Significant observational evidence of this phenomenon was recorded during the superstorm period of 10–11 May 2024 (Mother's Day solar storm). This superstorm period caused an increased vertical drift in the F region, leading the peak to rise above 300 km. The extreme conditions during this superstorm provided a rare opportunity to observe the dynamics of the ionosphere and validate our model. The observations during the superstorm period highlight the importance of understanding vertical drift dynamics and their impact on ionospheric behavior, especially during extreme space weather events.