Effects on atmospherics at 6 kHz and 9 kHz recorded at Tripura during the India-Pakistan Border earthquake

De, S. S.; De, B. K.; Bandyopadhyay, Bidhan C.; Paul, Suman; Haldar, D.P.; Bhowmick, A.; Barui, S.; Ali, R.

doi:10.5194/nhess-10-843-2010

Cited by 8 publications

(3 citation statements)

References 37 publications

(21 reference statements)

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“…Afterwards only case studies have been mainly done. Unusual variations of the intensity of the sferics received at 6 kHz and 9 kHz at Agartala, India (latitude, 23˚N; longitude, 91.4˚E) have been reported by [2] some days before an earthquake occurring on October 8, 2005 at Muzaffarabad, Pakistan (latitude, 34.53˚N; longitude, 73.58˚E). The number of sferics was highest on the day of the earthquake.…”

Section: Introductionmentioning

confidence: 99%

Is There an Earthquake Weather?

Parrot¹,

Pinçon²

2020

OJER

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The aim of this study is to check if there is a relationship between the seismic activity and the whistlers observed by the micro-satellite DEMETER. Whistlers are the waves emitted by lightning strokes during thunderstorm activity. They use to propagate in the Earth-ionosphere waveguide but also in the ionosphere and the magnetosphere mainly along the magnetic field lines. Due to this reason we have checked the whistler occurrence not close to earthquake epicenters but close to the magnetically conjugate point of these epicenters at the satellite altitude. The number of whistlers is given by a neural network in operation onboard the satellite. It appears that the whistler amplitude is attenuated at the satellite altitude around the magnetic equator. It is why we have removed the earthquakes occurring at low geomagnetic latitudes in the statistic. The whistler rate is normalized with a background value to take into account the seasons and the epicenter locations. A superposed epoch method is used to display the results between −15 and +5 days around the earthquake day and up to 1000 km from the conjugate point of the epicenters. It is shown that the whistler rate is higher the day before the earthquake at a distance less than 200 km. It would be unrealistic to believe in the possibility to use this study for earthquake prediction because everyday thunderstorm activity reliably masks seismic effects. But it is further evidence that there is a lithosphere-atmosphere-ionosphere coupling at the time of the seismic activity.

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Section: Introductionmentioning

confidence: 99%

Is There an Earthquake Weather?

Parrot¹,

Pinçon²

2020

OJER

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“…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]. Proper knowledge about the nature of propagation of VLF sferics is also of special interest for a number of reasons, like estimation of global lighting activity, correlation studies between lighting activity, global temperature and climate change [ Rodger et al , 2006; De et al , 2006; Guha and De , 2009; Dowden et al , 2008; Ming et al , 2005].…”

Section: Introductionmentioning

confidence: 99%

“…Regular studies of VLF sferics at different discrete frequencies are performed at the laboratory of Department of Physics, Tripura University [ De et al , 2005; Guha and De , 2009; De et al , 2010a, 2010b]. On the occasion of the two recent solar eclipses, identical experimental arrangement was made to investigate the effects of the eclipses on the spectral character of VLF sferics in the equatorial region.…”

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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