Ultra low frequency

Ultra low frequency
Frequency range	0.3 to 3 kHz
Wavelength range	1,000 to 100 km

Ultra low frequency (ULF) is the ITU designation^[1] for the frequency range of electromagnetic waves between 300 hertz and 3 kilohertz, corresponding to wavelengths between 1,000 to 100 km. In magnetosphere science and seismology, alternative definitions are usually given, including ranges from 1 mHz to 100 Hz,^[2] 1 mHz to 1 Hz,^[3] and 10 mHz to 10 Hz.^[4]

Many types of waves in the ULF frequency band can be observed in the magnetosphere and on the ground. These waves represent important physical processes in the near-Earth plasma environment. The speed of the ULF waves is often associated with the Alfvén velocity that depends on the ambient magnetic field and plasma mass density.

This band is used for communications in mines, as it can penetrate the earth.^[5]

^ "Rec. ITU-R V.431-7, Nomenclature of the frequency and wavelength bands used in telecommunications" (PDF). ITU. Archived from the original (PDF) on 31 October 2013. Retrieved 20 February 2013.
^ V. A. Pilipenko, "ULF waves on the ground and in space", Journal of Atmospheric and Terrestrial Physics, Volume 52, Issue 12, December 1990, pp. 1193–1209, ISSN 0021-9169, doi:10.1016/0021-9169(90)90087-4.
^ T. Bösinger and S. L. Shalimov, "On ULF Signatures of Lightning Discharges", Space Science Reviews, Volume 137, Issue 1, pp. 521–532, June 2008, doi:10.1007/s11214-008-9333-4.
^ O. Molchanov, A. Schekotov, E. Fedorov, G. Belyaev, and E. Gordeev, "Preseismic ULF electromagnetic effect from observation at Kamchatka", Natural Hazards and Earth System Sciences, Volume 3, pp. 203–209, 2003
^ HF and Lower Frequency Radiation - Introduction Archived 2005-11-09 at the Wayback Machine

[ITU_Nomenclature-1] "Rec. ITU-R V.431-7, Nomenclature of the frequency and wavelength bands used in telecommunications" (PDF). ITU. Archived from the original (PDF) on 31 October 2013. Retrieved 20 February 2013.

[2] V. A. Pilipenko, "ULF waves on the ground and in space", Journal of Atmospheric and Terrestrial Physics, Volume 52, Issue 12, December 1990, pp. 1193–1209, ISSN 0021-9169, doi:10.1016/0021-9169(90)90087-4.

[3] T. Bösinger and S. L. Shalimov, "On ULF Signatures of Lightning Discharges", Space Science Reviews, Volume 137, Issue 1, pp. 521–532, June 2008, doi:10.1007/s11214-008-9333-4.

[4] O. Molchanov, A. Schekotov, E. Fedorov, G. Belyaev, and E. Gordeev, "Preseismic ULF electromagnetic effect from observation at Kamchatka", Natural Hazards and Earth System Sciences, Volume 3, pp. 203–209, 2003

[5] HF and Lower Frequency Radiation - Introduction Archived 2005-11-09 at the Wayback Machine

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