Seasonal variations of globally measured ELF/VLF radio noise

Chrissan, D. A.; Fraser–Smith, A. C.

doi:10.1029/96rs01930

Cited by 52 publications

(44 citation statements)

References 7 publications

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“…Other data sets at similar frequencies but different locations have also been studied. Chrissan and Fraser-Smith [1996] analyzed seasonal variations from four locations around the world. The variations were largely inferred as lightning source changes, and although subionospheric propagation effects were considered, no estimation of the possible effects was made.…”

Section: Introductionmentioning

confidence: 99%

Diurnal and annual variations in 10‐kHz radio noise

Clilverd¹,

Watkins²,

Smith³

et al. 1999

Radio Science

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Abstract. It is shown that the investigation of lightning activity levels, using very low frequency radio emissions near 10 kHz, needs to take into account the significant influences of subionospheric propagation. Ten-kilohertz spectral power measurements made at Halley, Antarctica (76øS, 26øW), show at least two significant periodicities. The largest variation (10 dB) is due to the diurnal cycle and is strongly dominated by South American thunderstorm activity levels. The effect of African thunderstorm activity is observable in the diurnal variation plots but is strongly reduced by disadvantageous propagation conditions. The analysis suggests that given two identical tropical source regions, one situated east and one situated west, of a polar receiver site, the region to the west will tend to dominate the diurnal variation. The smaller annual variation at Halley (3 dB) can be explained by the improved subionospheric propagation conditions during the Southern Hemisphere winter counterbalancing the seasonal effects of decreased source activity in South America.

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Section: Introductionmentioning

confidence: 99%

Diurnal and annual variations in 10‐kHz radio noise

Clilverd¹,

Watkins²,

Smith³

et al. 1999

Radio Science

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“…From the 1980s to the 1990s, Stanford University organized the monitoring of the atmospheric noise from 10 Hz to 32 kHz in the eight sites global wide that lasted several years continuously (Chrissan et al 1997;Chrissan 1998). The observation data from four sites were published in the two reports (Chrissan andFraser-Smith 1996a, 1996b).…”

Section: Atmospheric Noise In Slf/elf Rangesmentioning

confidence: 97%

“…The main source of atmospheric noise in SLF/ELF ranges is the lightening discharge (Feldman 1972;Enge and Sawate 1988;Meloni et al 1992;Chrissan and Fraser-Smith 1996a). In the industrial or urban area, the variety of human activity also creates significant local interference in SLF/ELF ranges, especially around power stations and power transmission lines.…”

Section: Atmospheric Noise In Slf/elf Rangesmentioning

confidence: 99%

Historical and Technical Overview of SLF/ELF Electromagnetic Wave Propagation

Pan¹,

Li²

2013

Advanced Topics in Science and Technology in China

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In general, very low frequency (VLF) refers to electromagnetic waves with frequencies from 3 kHz to 30 kHz; ultra low frequency (ULF) refers to frequency range between 300 Hz to 3 kHz; the frequency range of 30 Hz to 300 Hz is defined as super low frequency (SLF); and the frequency below 30 Hz is referred to as extremely low frequency (ELF). In some early studies, alternative definitions may have been used with frequency range of 3 Hz to 3 kHz generally referred to ELF. In this book, the emphasis is on SLF (30-300 Hz) and ELF (below 30 Hz) ranges, using the MKS system of units and the time dependency e −iωt . Medium Characteristics of SLF/ELF Wave PropagationDue to the long wavelength, SLF/ELF waves, when excited and propagated on and near the Earth's surface, will cover lithosphere, atmosphere and ionosphere, whose electromagnetic characteristics differ significantly in their propagation paths. The permeability of the atmosphere and ionosphere is approximately μ 0 , the permeability in free space, as well as that of the lithosphere, except in the regions that are rich in iron, nickel, cobalt, etc. Therefore, the permeability of the lithosphere can be also treated as μ 0 , if neither the transmitter nor the receiver is located in mineral-rich areas. The atmosphere is a non-conductive medium with negligible conductivity, whose permittivity is close to ε 0 , the permittivity of free space. While the lithosphere is conductive, the conductivity of sea water σ sea is in the range of 2.5-5.5 S/m, and the conductivity σ g of rock and soil in the range of 10 −2 -10 −4 S/m. The dielectric constant ε r of the lithosphere does not have large effects on the propagation of SLF/ELF waves.The ionosphere is composed of partially ionized gas, which includes electrons, ions, and electrically neutral particles, above 70 km or so from the sea level. The electrons and ions make the ionosphere conductive, thus the majority of the energy of the incident VLF/SLF/ELF waves will be reflected by the ionosphere. When both the transmitter and the receiver are located in the space between the ground and the W. Pan, K. Li, Propagation of SLF/ELF Electromagnetic Waves,

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“…From the 1980s to the 1990s, the monitoring of the atmospheric noise from 10 Hz to 32 kHz in the eight ground-based sites was carried out by Stanford University. With monitoring for several years, some observation data of the four sites and analyses were summarized in the two reports (Chrissan and Fraser-Smith 1996a;Chrissan 1998). Stanford University announced that the four sites were located at Arrival Heights (77.80°S, 193.30°W) in the South Pole, Dunedin (45.80°S, 189.50°W) in New Zealand, the Sondrestromford (67.00°N, 50.10°W) in Greenland, and Stanford (37.40°N, 122.20°W) in California.…”

Section: Speculation Of Global Atmospheric Noise Distributions In Slfmentioning

confidence: 99%

Atmospheric Noises in SLF/ELF Ranges

Pan¹,

2013

Advanced Topics in Science and Technology in China

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Seasonal variations of globally measured ELF/VLF radio noise

Cited by 52 publications

References 7 publications

Diurnal and annual variations in 10‐kHz radio noise

Diurnal and annual variations in 10‐kHz radio noise

Historical and Technical Overview of SLF/ELF Electromagnetic Wave Propagation

Atmospheric Noises in SLF/ELF Ranges

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