1. The diurnal variation of E layer is relatively smooth.

2. E0030 E region That part of the ionosphere in which the E layer tends to form.

3. E0020 E layer Layer of the ionosphere exhibiting one or several maxima of electron density, at about 110 km.

4. E0040 Es layer Sporadic E layer Intermittent layer of the ionosphere, of limited horizontal extent, in the E region.

5. From 1941 to 1942 at Cologne ionospheric interferences have been observed, which showed a specially favoured flow from NNE in the E-layer.

6. Very low frequencies (VLF: 3–30 kHz), and extremely low frequencies (ELF: <3 kHz) are reflected at the ionospheric D- and lower E-layer.