Propagation

Watt, A. D.; Croghan, R.D.

doi:10.1016/b978-0-08-012313-4.50007-4

Cited by 4 publications

(2 citation statements)

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“…Earth‐ionosphere spherical waveguide models give the best description of long‐distance VLF transmission (>2 Mm) [ Wait , 1959; Watt and Crogham , 1967; Harth , 1982, and references therein]. The upper boundary of the waveguide, the daytime ionosphere D region, is very sensitive to the excess ionizing radiation from solar flares, which produce a net reduction of the waveguide height.…”

Section: Introductionmentioning

confidence: 99%

“…Phase sensitive receivers detect the VLF signals produced by a number of fixed transmitters at different locations in the world, used for navigation support. High‐precision frequency standards, such as atomic clocks, control the VLF receivers, allowing high accuracy in phase advance measurements, depending on the time integration [ Chilton et al , 1963; Crombie , 1965; Watt and Crogham , 1967; Harth , 1982, and references therein]. The most common VLF data available are time integrated by tens of seconds producing meaningful readings within a fraction of a microsecond.…”

Section: Introductionmentioning

confidence: 99%

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Solar flares not producing sudden phase advances

et al. 2002

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[1] We present a study of solar flares that do not produce disturbances in the low terrestrial ionosphere, detectable in very low frequency (VLF) low ionosphere propagation as sudden phase advances (SPA). We selected only flares with larger optical H-a importance (equal or larger than 1), occurred near the cycle 22 solar maximum (1987)(1988)(1989), at times when VLF data were available for long-distance propagation paths entirely illuminated by the Sun. For the 463 optical solar flares selected, we found that 18.8% had no measurable effects on the lower ionosphere. Inversely, all measured SPAs did have a solar counterpart, optical (such a subflare) and/or X-ray fluxes. Among the H-a flares that do not produce measurable disturbances in the low terrestrial ionosphere, there is a surprising selection for events occurred at the solar limbs. On the other hand, the X-ray flux for the H-a flares selected, obtained from GOES for the bands 0.5-4 Å and 1-8 Å exhibited a rather scattered correlation with the SPAs amplitudes. GOES X-rays fluxes for H-a flares not producing SPAs extend over 2-3 orders of magnitude. These results may suggest real physical distinctions between events. Possible explanations suggest the existence of a directional trend for the soft X-ray produced in flares possibly combined with the blockage of ionizing X rays behind the solar limbs.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Solar flares not producing sudden phase advances

et al. 2002

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Synopsis of the historical development of Schumann resonances

Besser

2007

Radio Science

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[1] The life and work of Winfried Otto Schumann and the historical development of the main ideas leading to the hypothesis of Earth-ionosphere cavity electromagnetic oscillations are reviewed. The so-called Schumann resonances are a set of frequencies of electromagnetic waves in the natural cavity formed by a planet's (moon's) surface and its ionosphere, in the extremely low frequency (ELF) range, caused by natural electrical activity of the planet (moon) and/or its atmospheric environment. Additionally, the reception of his work by the contemporary scientific community as well as the experimental evidence for the postulated ELF resonance oscillations is described.

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