Editing Solar cycle (section)

==== Radio communication ====
{{Main|Skywave}}
Skywave modes of radio communication operate by bending ([[refracting]]) radio waves ([[electromagnetic radiation]]) through the [[Ionosphere]]. During the "peaks" of the solar cycle, the ionosphere becomes increasingly ionized by solar photons and [[cosmic rays]]. This affects the [[Radio propagation|propagation]] of the radio wave in complex ways that can either facilitate or hinder communications. Forecasting of skywave modes is of considerable interest to commercial [[Marine (ocean)|marine]] and [[aircraft]] [[communications]], [[amateur radio operators]] and [[shortwave]] [[Broadcasting|broadcasters]]. These users occupy frequencies within the [[High Frequency]] or 'HF' radio spectrum that are most affected by these solar and ionospheric variances. Changes in solar output affect the [[maximum usable frequency]], a limit on the highest [[frequency]] usable for communications.