A study of data from the cylindrical electrostatic probe and the topside sounder aboard the Alouette 2 satellite reveals the existence of nighttime Ne enhancements at mid-latitudes, at altitudes 1,000-3,000km. The peaks seem to approach the equator with increasing altitude, and appear to lie on a specific set of geomagnetic field lines. The intensity and location of these nocturnal Ne peaks, as well as the electron density in the entire low-to mid-latitude range, show a marked dependence on

more »

... agnetic longitude. These observations are interpreted in terms of field-aligned flow of thermal plasma from the protonosphere above 3,000 km in the presence of a westward electric field at L-2.