The E-layer is part of the ionosphere that influences the propagation of radio waves, especially in the mediumwave and lowershortwave bands. It is also called the Heaviside layer or the Kennelly-Heaviside layer, after physicists Edwin Kennelly and Oliver Heaviside.

During the daytime the solar wind presses this layer closer to the Earth, thereby limiting how far it can reflect radio waves. On the night side of the Earth, the solar wind drags the ionosphere further away, thereby greatly increasing the range which radio waves can travel by reflection, called skywave.

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