ENHANCED VELOCITIES AND A SHEAR IN DAYTIME E(SQ) OVER KWAJALEIN AND THEIR RELATIONSHIP TO 150-KM ECHOES OVER THE DIP EQUATOR

We present the first evidence of enhanced irregularity-drift velocitie s and a velocity shear in the daytime E region at 4.3 degrees N dip la titude. These features, found in radar measurements from Kwajalein dur ing q-type sporadic E (E(sq)) events, are interpreted in terms of a po larization electric field that develops in response to the presence of latitudinal gradients in field-line-integrated conductivity caused by spbradic-E layers. Because the E region over Kwajalein connects direc tly 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.