VLF signals in summer and winter in the Indian sub-continent using multi-station campaigns

Chakrabarti, Sandip K.; Mondal, S. K.; Sasmal, Sudipta; Pal, Sujay; Basak, Tamal; Bhowmick, Debashis; Ray, Suman; Maji, Surya Kanta; Nandi, A.; Yadav, Vipin K.; Kotoch, T. B.; Khadka, Balaram; Giri, Kinsuk; Garain, Sudip K.; Choudhury, A. K.; Partra, N. N.; Nasser, Iqbal,

doi:10.1007/s12648-012-0070-x

Cited by 39 publications

(10 citation statements)

References 14 publications

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“…We can easily see that in some places the signals are enhanced and in some others the signals are reduced. These results match almost exactly with the observed results [3][4].…”

Section: Propagation Path and The Resultssupporting

confidence: 92%

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Modeling VLF signal amplitudes over Indian sub-continent during the total solar eclipse

Pal

Basak

Chakrabarti

2011

2011 XXXth URSI General Assembly and Scientific Symposium

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We present the simulation results incorporating the effect of solar eclipse (22nd July, 2009) on VLF signals for West-East propagation path with respect to Indian Navy transmitter (VTX) assuming a Gaussian variation of the ionospheric reflection height as a function of propagation distance along the transmitter-receiver great circle path. We use both the wave-hop and the Long Wave Propagation Capability (LWPC) codes. Using wave-hop theory we found that a reasonable matching between the observed and simulated results are achieved.

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“…We can easily see that in some places the signals are enhanced and in some others the signals are reduced. These results match almost exactly with the observed results [3][4].…”

Section: Propagation Path and The Resultssupporting

confidence: 92%

“…Chakrabarti et al [3][4] found both positive and negative fractional changes in VLF amplitudes roughly in the same propagation direction from the VTX transmitter during the total solar eclipse 22 July, 2009. To reproduce the observed features here we use both wave-hop and LWPCv21 programs.…”

Section: Introductionmentioning

confidence: 94%

Modeling VLF signal amplitudes over Indian sub-continent during the total solar eclipse

Pal

Basak

Chakrabarti

2011

2011 XXXth URSI General Assembly and Scientific Symposium

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“…In Chakrabarti et al [], it was pointed out that there is a strong nonreciprocity of east to west and west to east propagation [ Burgess , ; Crombi , ] as observed for the entire landmass of India. It was observed that the daytime signal attenuation is larger than that at nighttime for the west to east propagation, and for the east to west propagation, the nighttime attenuation is larger than daytime.…”

Section: Observationmentioning

confidence: 99%

Modeling of long‐path propagation characteristics of VLF radio waves as observed from Indian Antarctic station Maitri

2015

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Propagation of very low frequency (VLF) radio signal through the Earth‐ionosphere waveguide depends strongly on the plasma properties of the ionospheric D layer. Solar extreme ultraviolet radiation plays the central role in controlling physical and chemical properties of the lower ionospheric layers and hence determining the propagation characteristics of a VLF signal. The nature of interference among different propagating modes varies widely with the length of the propagation path. For a very long path, exposure of solar radiation and thus the degree of ionization vary by a large amount along the path. This influences the VLF signal profile by modulating the sky wave propagation. To understand the propagation characteristics over such a long path, we need a thorough investigation of the chemical reactions of the lower ionosphere which is lacking in the literature. Study of radio signal characteristics in the Antarctic region during summer period in the Southern Hemisphere gives us a unique opportunity to explore such a possibility. In addition, there is an extra feature in this path—the presence of solar radiation and hence the D region for the whole day during summer in at least some sections of the path. In this paper, we present long‐distance propagation characteristics of VLF signals transmitted from VTX (18.2 kHz) and NWC (19.8 kHz) transmitters recorded at the Indian permanent station Maitri (latitude 70° 45′S, longitude 114° 40′E) in 2007–2008. A very stable diurnal variation of the signal has been obtained with no signature of nighttime fluctuation due the presence of 24 h of sunlight. Using ion production and recombination profiles by solar irradiance and incorporating D region ion chemistry processes, we calculate the electron density profile at different heights. Using this profile in the Long Wavelength Propagation Capability code, we are able to reproduce the amplitude of VLF signal.

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“…Effects of various solar (flare, eclipse) (Mitra 1974;Grubor et al 2008;Chakrabarti et al 2012;Clilverd et al 2001) and extra terrestrial (Soft Gamma Ray Repeater, Gamma Ray Bursts etc.) Mondal et al 2012;Inan et al 2007) events can perturb the physical and chemical properties of ionospheric layers.…”

Section: Introductionmentioning

confidence: 99%

Studies of seismo-ionospheric correlations using anomalies in phase of very low frequency signal

Pal

Sasmal

Chakrabarti

2017

Geomatics, Natural Hazards and Risk

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We present the results of the statistical analysis of very low frequency (VLF) signal transmitted from NWC transmitter (latitude 21.8 S, longitude 114.15 E) at 19.8 kHz received at Ionospheric and Earthquake Research Centre (IERC) (latitude 22.50 N, longitude 87.79 E). We analyse the phase of VLF signal for the whole year 2011 and compute the sunrise and sunset terminator time from it. We observe unusual shift of these sunrise and sunset terminator time during seismic events for which the earthquake epicentres are in India and its subcontinent region. We calculate the total energy accumulation by all those earthquakes for a single day and compute the effective magnitude of all the earthquakes for that day which behaves as a single quake. We compute a cross correlation between fluctuation in terminator time shifts from the normal value with effective magnitude of earthquake. We found that the unusual fluctuations in terminator time are well correlated with earthquake magnitude and the fluctuation is maximum on two days prior to earthquake events.

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VLF signals in summer and winter in the Indian sub-continent using multi-station campaigns

Cited by 39 publications

References 14 publications

Modeling VLF signal amplitudes over Indian sub-continent during the total solar eclipse

Modeling VLF signal amplitudes over Indian sub-continent during the total solar eclipse

Modeling of long‐path propagation characteristics of VLF radio waves as observed from Indian Antarctic station Maitri

Studies of seismo-ionospheric correlations using anomalies in phase of very low frequency signal

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