Rocket measurements of theE-region electron concentration distribution in the vicinity of the geomagnetic equator

Six rocket measurements of the E-region electron concentration distribution were conducted in the vicinity of the geomagnetic equator near the coast of Peru. The instrumentation consisted of the two-frequency propagation experiment and a Langmuir probe. Four of the flights occurred near local noon on separate days. There is little variation between electron concentration profiles. No sporadic E layer was observed, although q-type sporadic E was visible on ionograms taken simultaneously with the flights. The remaining two flights were conducted on separate nights. The electron concentration height profiles suggest that on certain nights or, alternately, after midnight the equatorial E region above 150 km is under F-region control. The existence of a downward drift is supported by the measurements. Below 150 km, the existence of a layer at night has been established. The layer centered at 105 km had a peak density of 2 × 10³ cm−3 on March 26, 1965, and 1.5 × 104 cm−3 on March 18, 1965. It is similar to that formed at midlatitudes.