Very low frequency atmospheric radio noise field intensities

Sen, A. K.; Bhattacharya, Aniruddha; Sarkar, S. K.

doi:10.1007/bf02258038

Cited by 4 publications

(2 citation statements)

References 2 publications

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“…The arrival of lightning sferics may occur directly or by reflection from the D-region of the ionosphere [6]. The amplitude of VLF sferics shows diurnal variation depending on the location of the receivers [7,8]. The diurnal nature of VLF electric field atmospherics may not always show 'Carnegie curve' in some areas of the globe depending on the atmospheric weather at the receiving location [9,10].…”

Section: Introductionmentioning

confidence: 99%

Impact of Two Tropical Cyclones on the Radio Atmospherics Observed Using VLF Receivers

Pal¹,

Das

Sen³

et al. 2021

Preprint

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The response of electric field intensity of VLF radio atmospherics during two tropical cyclones Fani (May 2019) and Amphan (May 2020) has been presented in this paper. VLF radio atmospherics (or VLF sferics) received at Coochbehar (CHB) and Kolkata (CUB) at three discrete frequencies (4 kHz, 7 kHz, and 9 kHz) showed clear amplitude anomalies with respect to the reference level during the two cyclonic storms. This is explained using the electrical structure and distribution of cloudto-ground lightning associated with the cyclones. Effects of 'local lightning' and 'distant lightning' have been identified for both the CUB and CHB receivers. Field intensity of VLF sferics at CUB station was found to get enhanced for both types of lightning events. But the intensity of VLF sferics at CHB station was found to be reduced for 'distant lightning' and enhanced for 'local lightning', possible reasons of which are also explained.

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Section: Introductionmentioning

confidence: 99%

Impact of Two Tropical Cyclones on the Radio Atmospherics Observed Using VLF Receivers

Pal¹,

Das

Sen³

et al. 2021

Preprint

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“…Long distance propagation of such electromagnetic waves is controlled mainly by the status of the lower ionosphere and conductivity of the Earth's surface [ De et al , 2010a; Cummer et al , 1998]. Sferics are generally known to have a typical diurnal variation [ De and Sarkar , 1996; Bhattacharya et al , 1980; Sen et al , 1982] which shows variations during various geophysical events, thunderstorm activities, solar events, earthquake etc. [ De and Sarkar , 1995; Bhattacharya et al , 1997; De et al , 2010b].…”

Section: Introductionmentioning

confidence: 99%

Spectral character of VLF sferics propagating inside the Earth‐ionosphere waveguide during two recent solar eclipses

Guha

Choudhury

et al. 2012

J. Geophys. Res.

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Effects of solar eclipses on the propagation characteristics of worldwide VLF sferics from lightning activity require more investigation. An attempt was made on the occasion of two solar eclipses during 22nd July, 2009 and 15th January, 2010 to study the effects of the two eclipses on the propagation characteristics of VLF sferics in the Earth‐ionosphere waveguide. Identical experimental setups were used to study the VLF sferics during the two eclipse events. The spectral character of VLF sferics propagating inside the waveguide is studied at a fixed receiver location (23.75°N, 91.25°E) at six discrete frequencies in between 3 and 20 kHz. During both the eclipse events, it is observed that VLF sferics at all the six discrete frequencies is increased from the mean normal average ambient level. The increment peaks around 10–12 kHz with an overall increment of 6.4 dB with respect to its ambient level. The VLF spectral character of enhancement of sferics show similar characters in two eclipses. The percentage decrease in electron density using standard modeling equations is found to be 90% at the height of 71 km for both the eclipses, supporting linear variation of electron density with solar radiation at the D‐region of the ionosphere. The results are explained qualitatively on the basis of a decrease in electron density at the lower ionosphere modifying the reflection coefficient which affected the propagation of VLF sferics in Earth‐ionosphere waveguide during eclipsed condition.

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Techniques and Instruments for the Measurement of Atmospheric Noise

Bhattacharya

1983

IETE Journal of Research

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Very low frequency atmospheric radio noise field intensities

Cited by 4 publications

References 2 publications

Impact of Two Tropical Cyclones on the Radio Atmospherics Observed Using VLF Receivers

Impact of Two Tropical Cyclones on the Radio Atmospherics Observed Using VLF Receivers

Spectral character of VLF sferics propagating inside the Earth‐ionosphere waveguide during two recent solar eclipses

Techniques and Instruments for the Measurement of Atmospheric Noise

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