Editing Terminator (solar) (section)

===Grey-line radio propagation===
Strength of [[radio propagation]] changes between day- and night-side of the [[ionosphere]]. This is primarily because the [[D region|D layer]], which absorbs [[High frequency|high frequency signals]], disappears rapidly on the dark side of the terminator, whereas [[E region|the E]] and [[F region|F layer]]s above the [[D region|D layer]] take longer to form.<ref name=Weiss_2011>Adrian Weiss. (2011). ''Ionospheric Propagation, Transmission Lines, and Antennas for the QRP DXer'', pp.&nbsp;1–16, 1-22&ndash;1-24. Green Valley, AZ: Milliwatt QRP Books.</ref> This time-difference puts the [[ionosphere]] into a unique intermediate state along the terminator, called the "grey line".<ref name=dx_qsl_net>{{Cite web|url=http://dx.qsl.net/propagation/|title=Propagation}}</ref>

[[Amateur radio]] operators take advantage of conditions along the terminator to perform long-distance communications. Called "gray-line" or "grey-line" [[Radio propagation|propagation]], this signal path is a type of [[Skywave|skywave propagation]]. Under good conditions, radio waves can travel along the terminator to [[Antipodes|antipodal]] points.<ref name=dx_qsl_net/>