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]
Some monitoring stations have reported that earthquakes are sometimes preceded by a spike in ULF activity. A remarkable example of this occurred before the 1989 Loma Prieta earthquake in California,[6] although a subsequent study indicates that this was little more than a sensor malfunction.[7] On December 9, 2010, geoscientists announced that the DEMETER satellite observed a dramatic increase in ULF radio waves over Haiti in the month before the magnitude 7.0 Mw2010 earthquake.[8] Researchers are attempting to learn more about this correlation to find out whether this method can be used as part of an early warning system for earthquakes.
Earth mode communicationsedit
ULF has been used by the military for secure communications through the ground. NATO AGARD publications from the 1960s detailed many such systems, although it is possible that the published papers left a lot unsaid about what actually was developed secretly for defense purposes. Communications through the ground using conduction fields is known as "Earth-Mode" communications and was first used in World War I. Radio amateurs and electronics hobbyists have used this mode for limited range communications using audio power amplifiers connected to widely spaced electrode pairs hammered into the soil. At the receiving end, the signal is detected as a weak electric current between a further pair of electrodes. Using weak signal reception methods with PC-based DSP filtering with extremely narrow bandwidths, it is possible to receive signals at a range of a few kilometers with a transmitting power of 10–100W and electrode spacing of around 10–50m.[citation needed]
^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 2005-11-09 at the Wayback Machine
^Fraser-Smith, Antony C.; Bernardi, A.; McGill, P. R.; Ladd, M. E.; Helliwell, R. A.; Villard, Jr., O. G. (August 1990). "Low-Frequency Magnetic Field Measurements Near the Epicenter of the Ms 7.1 Loma Prieta Earthquake" (PDF). Geophysical Research Letters. 17 (9): 1465–1468. Bibcode:1990GeoRL..17.1465F. doi:10.1029/GL017i009p01465. ISSN 0094-8276. OCLC 1795290. Retrieved December 18, 2010.
^Thomas, J. N.; Love, J. J.; Johnston, M. J. S. (April 2009). "On the reported magnetic precursor of the 1989 Loma Prieta earthquake". Physics of the Earth and Planetary Interiors. 173 (3–4): 207–215. Bibcode:2009PEPI..173..207T. doi:10.1016/j.pepi.2008.11.014.
^KentuckyFC (December 9, 2010). "Spacecraft Saw ULF Radio Emissions over Haiti before January Quake". Cambridge, Massachusetts: MIT Technology Review. Retrieved December 18, 2010.
External articlesedit
Tomislav Stimac, "Definition of frequency bands (VLF, ELF... etc.)". IK1QFK Home Page (vlf.it).
NASA live streaming ELF -> VLF Receiver
Amateur Radio Below 10 kHz "G3XBM's page on Earth Mode Communication"
Review of Earth Mode Communications ""
Radio communications within the Earth's crust "Abstract of article by Burrows written in 1963"
November 03, 2023
ultra, frequency, designation, frequency, range, electromagnetic, waves, between, hertz, kilohertz, corresponding, wavelengths, between, magnetosphere, science, seismology, alternative, definitions, usually, given, including, ranges, from, frequency, range0, k. 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 Ultra low frequencyFrequency range0 3 to 3 kHzWavelength range1 000 to 100 kmListening to 500 Hz signal of Ambrose Channel pilot cable in 1920Many 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 Alfven 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 Contents 1 Earthquakes 2 Earth mode communications 3 See also 4 References 5 External articlesEarthquakes editSome monitoring stations have reported that earthquakes are sometimes preceded by a spike in ULF activity A remarkable example of this occurred before the 1989 Loma Prieta earthquake in California 6 although a subsequent study indicates that this was little more than a sensor malfunction 7 On December 9 2010 geoscientists announced that the DEMETER satellite observed a dramatic increase in ULF radio waves over Haiti in the month before the magnitude 7 0 Mw 2010 earthquake 8 Researchers are attempting to learn more about this correlation to find out whether this method can be used as part of an early warning system for earthquakes Earth mode communications editULF has been used by the military for secure communications through the ground NATO AGARD publications from the 1960s detailed many such systems although it is possible that the published papers left a lot unsaid about what actually was developed secretly for defense purposes Communications through the ground using conduction fields is known as Earth Mode communications and was first used in World War I Radio amateurs and electronics hobbyists have used this mode for limited range communications using audio power amplifiers connected to widely spaced electrode pairs hammered into the soil At the receiving end the signal is detected as a weak electric current between a further pair of electrodes Using weak signal reception methods with PC based DSP filtering with extremely narrow bandwidths it is possible to receive signals at a range of a few kilometers with a transmitting power of 10 100 W and electrode spacing of around 10 50 m citation needed See also editExtremely low frequency Earth s field NMR Valery Troitskaya Through the earth mine communications Voice frequencyReferences edit 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 Bosinger 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 Fraser Smith Antony C Bernardi A McGill P R Ladd M E Helliwell R A Villard Jr O G August 1990 Low Frequency Magnetic Field Measurements Near the Epicenter of the Ms 7 1 Loma Prieta Earthquake PDF Geophysical Research Letters 17 9 1465 1468 Bibcode 1990GeoRL 17 1465F doi 10 1029 GL017i009p01465 ISSN 0094 8276 OCLC 1795290 Retrieved December 18 2010 Thomas J N Love J J Johnston M J S April 2009 On the reported magnetic precursor of the 1989 Loma Prieta earthquake Physics of the Earth and Planetary Interiors 173 3 4 207 215 Bibcode 2009PEPI 173 207T doi 10 1016 j pepi 2008 11 014 KentuckyFC December 9 2010 Spacecraft Saw ULF Radio Emissions over Haiti before January Quake Cambridge Massachusetts MIT Technology Review Retrieved December 18 2010 External articles editTomislav Stimac Definition of frequency bands VLF ELF etc IK1QFK Home Page vlf it NASA live streaming ELF gt VLF Receiver Amateur Radio Below 10 kHz G3XBM s page on Earth Mode Communication Review of Earth Mode Communications 1966 abstract about Earth Mode Comms by Ames Frazier and Orange Radio communications within the Earth s crust Abstract of article by Burrows written in 1963 Retrieved from https en wikipedia org w index php title Ultra low frequency amp oldid 1127745732, wikipedia, wiki, book, books, library,
