ELECTRON CONTENT OF LOW LATITUDE IONOSPHERE

The electron content of the ionosphere has been determined at latitudes of 5°S-35°S, during 354 transits of the satellite S-66 recorded at Rarotonga. In Winter the peak of the equatorial anomaly forms between 0700 and 0900 LT. It remains at a latitude of 8°S throughout the day, and decays slowly overnight. In Summer the peak forms between 0830 and 1030 LT, at a latitude of 10°S. It moves to 17°S by 1400 LT, returning to 10°S as it disappears near sunset. The size of the peak is about the same in both seasons, although the electron content has a seasonal variation of 3:1 at higher latitudes. There is a sharp transition from the approximately constant electron content,at medium latitudes to the rapidly increasing content near the equatorial zone. This transition point is at about 21°S in Winter, and 23°S in Summer. © 1969.