Editing Lightning (section)

====Radio frequency radiation====
{{further|Radio atmospheric signal|label1=Radio atmospheric|Whistler (radio)|label2=Whistler|Schumann resonances}}

Lightning discharges generate radio-frequency electromagnetic waves which can be received thousands of kilometers from their source. The discharge by itself is relatively simple short-lived [[dipole]] source that creates a single electromagnetic pulse with a duration of about 1 ms and a wide spectral density. 
In the absence in the nearby environment of materials with [[Permeability (electromagnetism)|magnetic]] or [[Permittivity|electrical]] interaction properties, at a large distances in a [[Near and far field|far field]] zone, the electromagnetic wave will be proportional to the second derivation of the discharge current.<ref>{{cite book|last1=Landau|first1=Lev D|author1-link=Lev Landau|last2=Lifshitz|first2=Evgeny M|author2-link=Evgeny Lifshitz|title=[[Course of Theoretical Physics|The Classical Theory of Fields]]|volume=2|edition=4th|publisher=Butterworth-Heinemann|date=1975|isbn=978-0-7506-2768-9}}</ref> This is what happens with high-altitude discharges or discharges over areas of a dry land.
{{multiple image
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 | image1=
 | caption1=A single unaffected discharge over a dry land.
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 | caption2=A discharge above conductive ground that induced local [[Eddy current]]s.
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 | caption3=A discharge above [[ocean]]ic waters triggered [[resonance]] oscillations.
 | footer=Electromagnetic signals in a 10 Hz to 4 kHz frequency range produced by three different lightning discharges occurring thousands of kilometers away from the same registering station.<ref>{{cite web |url=https://hmicom.com/Archive/X3PE2ANC|title=Electromagnetic field records taken August 2016 near Stewart BC, Canada.|last=Issinski|first=A.|date=2016-08-28}}</ref> The lightning's local environment altered the shape of the received [[Near and far field|far field]] signal.
}}
In other cases, the surrounding environment will change the shape of the source signal by absorbing some of its spectrum and converting it into a heat or re-transmitting it back as modified electromagnetic waves.<ref>{{cite book|last1=Landau|first1=Lev D|author1-link=Lev Landau|last2=Lifshitz|first2=Evgeny M|author2-link=Evgeny Lifshitz|last3=Pitaevskii|first3=Lev P|author3-link=Lev Pitaevskii|title=[[Course of Theoretical Physics|Electrodynamics of Continuous Media]]|volume=8|edition=2nd|publisher=Butterworth-Heinemann|date=1984|isbn=978-0-7506-2634-7}}</ref>