Editing Atmospheric diffraction (section)

==Radio wave propagation in the ionosphere==
{{see also|Ionospheric radio propagation}}

{{Disputed section|small=left|date=August 2023}}

The [[ionosphere]] is a layer of partially [[ionized]] [[gases]] high above the majority of the [[Earth]]'s [[atmosphere]]; these gases are ionized by [[cosmic rays]] originating on the sun.  When radio waves travel into this zone, which commences about 80 kilometers above the earth, they experience [[diffraction]] in a manner similar to the [[visible light]] phenomenon described above.<ref>[[Leonid M. Brekhovskikh]], ''Waves in Layered Media'' [[Academic Press]], New York, 1960)</ref> In this case some of the electromagnetic energy is bent in a large arc, such that it can return to the Earth's surface at a very distant point (on the order of hundreds of kilometers from the [[Broadcasting|broadcast]] source.  More remarkably some of this radio wave energy bounces off the Earth's surface and reaches the ionosphere for a second time, at a distance even farther away than the first time.  Consequently, a high powered [[transmitter]] can effectively broadcast over 1000 kilometers by using multiple "skips" off of the ionosphere.  And, at times of favorable atmospheric conditions good "skip" occurs, then even a low power transmitter can be heard halfway around the world.  This often occurs for "novice" radio amateurs "hams" who are limited by law to transmitters with no more than 65 watts.  The Kon-Tiki expedition communicated regularly with a 6 watt transmitter from the middle of the Pacific. For more details see the "communications" part of the "[[Kon-Tiki expedition]]" entry in Wikipedia.

An exotic variant of this radio wave propagation has been examined to show that, theoretically, the ionospheric bounce could be greatly exaggerated if a high powered spherical [[Acoustics|acoustical]] wave were created in the ionosphere from a source on earth.<ref>Michael Hogan, ''Ionospheric Diffraction of VHF Radio Waves'', ESL Inc., Palo Alto, California, IR-26 22 May 1967</ref>