Normal and abnormal E ‐region electron density profiles at a midlatitude station

The problems of measuring reliable E ‐region electron density vs. height profiles with a vertically pointing, pulsed incoherent scatter radar are discussed, and profiles from heights of 90 km upward observed at Malvern are presented. The minimum above h max E is more pronounced in winter than in summer, and the overall average density in the minimum is 92% of N max E . From the observational point of view, profiles showing an unresolved sporadic‐ E layer seem merely to be an extreme case of the normal type. Many layers are present in the E region at night; the behavior of these is erratic except for the principal layer centered just below 100 km, which may be meteoritic in origin. Incoherent scatter offers a new method of investigating the effects of solar flares in the 100 to 130 km range; observations taken during a flare, and also during a partial solar eclipse and on a magnetically disturbed day, are described.