Enhanced velocities and a shear in daytime Esq over Kwajalein and their relationship to 150 km echoes over the dip equator

Abstract

We present the first evidence of enhanced irregularity‐drift velocities and a velocity shear in the daytime E region at 4.3°N dip latitude. These features, found in radar measurements from Kwajalein during q‐type sporadic E (Esq) events, are interpreted in terms of a polarization electric field that develops in response to the presence of latitudinal gradients in field‐line‐integrated conductivity caused by sporadic‐E layers. Because the E region over Kwajalein connects directly to 150‐km altitude over the magnetic dip equator, we suggest that a similar polarization process is responsible for the so‐called 150‐km echoes that have been observed routinely by the Jicamarca radar.