Kennelly-Heaviside Layer

Also known as the E region or just as Heaviside Layer.

It is layer of ionised gas occuring at 90-150km in altitude, one of several layers in the ionosphere. It reflects medium-frequency radio waves and because of this reflection, radio waves can be propagated beyond the horizon.

Propagation is affected by time of day, season, and sunspot activity.

It's existence was announced in 1902 independently and almost simultaneously by the American electrical engineer [Arthur Edwin Kennelly]? (1861-1949) and the British physicist [Oliver Heaviside]? (1850-1925).