Dawn chorus (electromagnetic)

VLF spectrogram of electromagnetic chorus, as received by the Stanford University VLF group's wave receiver at Palmer Station, Antarctica. The chorus can be seen between 1000 Hz and 3000 Hz, sandwiched between components of sferics

The electromagnetic dawn chorus is an unexplained phenomenon that occurs most often at sunrise or shortly after, that (with the proper radio equipment) resembles the sound of the birds' dawn chorus. It is thought to be caused by high-energy electrons that get caught in the Van Allen radiation belts of the Earth's magnetosphere and fall to the Earth's surface in the form of audible radio waves. Dawn choruses occur more frequently during magnetic storms.

This phenomenon also occurs during aurorae, when it is termed an auroral chorus.

See also

• Auroral chorus
• Hiss (electromagnetic)
• Whistler (radio)

Further reading

• Robert A. Helliwell (2006 [1965]). Whistlers and Related Ionospheric Phenomena. Dover Publications, Inc. ISBN 0-486-44572-0. {{cite book}}: Check date values in: |year= (help)CS1 maint: year (link)
• Romero, R. (2008). Radio Nature. Potters Bar: Radio Society of Great Britain. pp. 39–40. ISBN 9781-9050-8638-2.

External links

• Stephen P. McGreevy's ground-based ELF-VLF recordings
• Natural VLF Radio - Sounds of Space Weather
• Space-Weather Sounds - the Mysterious and Beautiful Natural Radio Phenomena of Earth
• VLF Discussion Group