Very low frequency

About: Very low frequency is a research topic. Over the lifetime, 1540 publications have been published within this topic receiving 24233 citations. The topic is also known as: VLF.

Computer-Program Model for Predicting Horizontally and Vertically Polarized VLF Atmospheric Radio Noise at Elevated Receivers

Abstract: : A computer program has been developed that can predict horizontally and vertically polarized atmospheric radio noise at any altitude or location in the earth-ionosphere waveguide in the very-low-frequency (VLF) range from 10 to 30 kHz. The new program, HORNS, uses the outputs of two previously written programs, COMPWR and NOISLAN, which predict the vertical electric noise field at the ground. The HORNS program computes all the field components at any altitude using the vertical electric field at the earth's surface as a basis. Predicted values from several versions of the new model have been compared with presently available data. The results are encouraging, but more data are needed to test the model.

Non-stationary effects in wave-particle interactions during storm sudden commencements (SSC)

Abstract: Simultaneous observations of energetic electrons (16-300 keV) and ELF/VLF waves (200 Hz-3 kHZ) are analysed, that are obtained onboard GEOS 2 in the dayside magnetosphere during Storm Sudden Commencements (SSC's). The electron distribution exhibits a large temperature anisotropy, leading to the amplification of whistler waves. Wave particle interactions (WPI's) are studied by calculating the temperature anisotropy and the wave growth rate from one minute averages of the particle data. Following the SSC, an increase in the electron distribution anisotropy results in an increase of the wave spectral intensity Bf2. Oscillations with a period of 2-4 min are observed in the maximum intensity Bfmax2 that are in antiphase both with the corresponding growth rate and the anisotropy. This last effect is interpreted in terms of the quasilinear pitch-angle diffusion of the resonant electrons.

Extracting geoelectrical maps from vintage very-low-frequency airborne data, tipper inversion, and interpretation: A case study from northern Sweden

Abstract: In 1985, the mining company Luossavaara-Kiirunavaara Aktiebolag collected airborne very-low-frequency (VLF) data in northern Sweden. The operators stored only the vertical component and the total magnetic field, which at that time were believed to be sufficient for qualitative interpretation. Therefore, the data could not be directly used for quantitative tensor VLF processing and inversion. To avoid the costs of resurveying, we have developed a novel technique to estimate the tippers from the measured VLF data by computing anomalous and normal parts of the horizontal components of the magnetic field from two transmitters separately. Retrieval of the normal horizontal components was possible because one component of the horizontal magnetic field was used as the phase reference during the measurements. Additionally, we have determined how the approximate apparent resistivity suitable for data visualization can be computed from the components of the magnetic field assuming an average normal resistiv...

Very low-frequency radio waves drain Earth’s inner radiation belt of satellite-killing electrons

Abstract: A high-altitude nuclear explosion would swell the radiation belt and imperil the global positioning system and other satellites. VLF transmissions could forestall the damage.

Southern boundaries of ultraenergetic relativistic electron precipitations in several cases from 1982 to 1986 years

Abstract: We analyze the rare phenomenon of ultraenergetic relativistic electron (∼100 MeV) precipitation into the middle polar atmosphere prevalent under quiescent geophysical conditions. Such events have been established previously from ground-based radio wave measurements for two radio paths—one is purely auroral and the other is partly auroral—that have a mutual point of signal reception. We solve an inverse very low frequency wave problem of the second type using these particular paths. The solution gives a linear scale of the northern part of radio path, which has been disturbed by the ultraenergetic relativistic electron precipitations. By such a way the effective latitudes of southern boundaries for several precipitation events, published earlier, were determined. Nearly circular shape of equatorward cutoff at ∼61°magnetic latitude without day-night asymmetry supports that ultraenergetic relativistic electron precipitation is due to precipitation of very high energy electrons coming from outer space.