Editing Kennelly–Heaviside layer (section)

{{short description|Layer of the Earth's ionosphere}}
{{more citations needed|date=September 2015}}
[[File:Ionosphere Layers en.svg|thumb|Layers of the [[ionosphere]].  The Kennelly–Heaviside layer is the E region]]
The '''Heaviside layer''',<ref name= Griffiths /><ref name="Marchant1916" /> sometimes called the '''Kennelly–Heaviside layer''',<ref name="McAdie1925" /><ref>{{cite journal|title=Atmospheric Pressure and the Ionisation of the Kennelly-Heaviside Layer|journal=[[Nature (journal)|Nature]]|first=D. F.|last=Martyn|year=1934|volume=133|issue=3356|page=294|issn=0028-0836|doi=10.1038/133294b0|bibcode=1934Natur.133R.294M|s2cid=684206|doi-access=free}}</ref> named after [[Arthur E. Kennelly]] and [[Oliver Heaviside]], is a layer of [[ionisation|ionised]] [[gas]] occurring roughly between 90km and 150&nbsp;km (56 and 93&nbsp;mi) above the ground &mdash; one of several layers in the [[Earth]]'s [[ionosphere]]. It is also known as the '''E region'''.  It reflects [[mediumwave|medium-frequency]] [[radio wave]]s.  Because of this reflective layer, radio waves radiated into the sky can return to Earth beyond the [[horizon]].  This "[[skywave]]" or "skip" propagation technique has been used since the 1920s for radio communication at long distances, up to transcontinental distances.

Propagation is affected by the time of day. During the daytime the [[solar wind]] presses this layer closer to the Earth, thereby limiting how far it can reflect radio waves.  Conversely, on the night ([[windward and leeward|lee]]) side of the Earth, the solar wind drags the ionosphere further away, thereby greatly increasing the range which radio waves can travel by reflection. The extent of the effect is further influenced by the [[season]], and the amount of [[sunspot]] activity.