Regular Behaviour of the Field Intensity of VLF Atmospherics over Calcutta

Bhattacharya, Asit Baran; Sarkar, S.; Sen, Arnab

doi:10.1080/03772063.1980.11452138

Cited by 3 publications

(4 citation statements)

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“…As a result, the discharges within the cloud decreases leading to the observed SFA effect. It may be mentioned here that the general view of most of the workers [2,11 ] is that the precipitation plays a major role in the process of charge separation within clouds. The small flat portion, i.e.…”

Section: Discussionmentioning

confidence: 96%

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On some characteristics of tropical atmospherics due to monsoon clouds

Sarkar

Bhattacharya

Sen

1982

Arch. Met. Geoph. Biocl. A.

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SummaryThe field intensity of VLF-atmosphefics recorded over the tropical station, Calcutta (22°34'N, 88°24'E) occasionally exhibit a characteristic fall in association with the ground rainfall during monsoon months. The sudden fall is followed by a pause and a subsequent recorvery thus forming a clipped saw-tooth like appearance. The occurrences and magnitudes of the fall are predominant at 20 kHz in the VLF-band. They mostly occur around local noon and midnight hours. Zusammenfassung Ober Charakteristiken tropischer Atmospherics aus MonsunwolkenDie Feldintensitgt der VLF-Atmospherics, die fiber Calcutta registriert wurde, zeigt gelegenttich einen charakteristischen Abfall in Verbindung mit Regen in den MonsunMonaten. Auf den pl6tzlichen AbfaU folgt eine Unterbrechung und darauf eine Wiederherstellung, so daft sich eine s~igezahnartige Form in der Registrierkurve bildet. Das Vorkommen und die Gr6fien des Abfalls iiberwiegen bei 20 kHz im VLF-Band. Am h~ufigsten kommt der AbfaU um Mittag und um Mittemacht vor.

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Section: Discussionmentioning

confidence: 96%

“…It is known that the level of atmospherics in Calcutta during the monsoon months becomes very high in comparison to that of the other seasons of the year [2]. The large increase in the monsoon season is mostly due to the active local sources originating from the sea level disturbances, like depression, in the Bay of Bengal [6,9].…”

Section: Discussionmentioning

confidence: 99%

On some characteristics of tropical atmospherics due to monsoon clouds

Sarkar

Bhattacharya

Sen

1982

Arch. Met. Geoph. Biocl. A.

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“…A photograph of the typical record of |FIA observed at the three frequencies is shown in Fig. 1 which shows all the regular variations [4,5 ]. These are: sunrise effect (A), first minimum (B), recovery effect (C), morning minimum (D), afternoon maximum (E), late afternoon minimum (F) and night maximum (G).…”

Section: Recording Of Datamentioning

confidence: 99%

Very low frequency atmospheric radio noise field intensities

Sen

Bhattacharya

Sarkar

1982

Arch. Met. Geoph. Biocl. A.

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SummarySimultaneous observations of the field strength of atmospheric radio noise at three harmonically related frequencies in the VLF band for a period of two years from October 1976 to September 1978 have been analyzed to explore the frequency spectrum of atmospherics. The results have been shown for different months and seasons of the year and interpreted in terms of source activity and propagation effect.

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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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Regular Behaviour of the Field Intensity of VLF Atmospherics over Calcutta

Cited by 3 publications

References 1 publication

On some characteristics of tropical atmospherics due to monsoon clouds

On some characteristics of tropical atmospherics due to monsoon clouds

Very low frequency atmospheric radio noise field intensities

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

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