On the use of Very Low Frequency transmitter data for remote sensing of atmospheric gravity and planetary waves

Pal, Sujay; Chakraborty, Suman; Chakrabarti, Sandip K.

doi:10.1016/j.asr.2014.11.023

Cited by 20 publications

(15 citation statements)

References 27 publications

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“…They advocated that these oscillations arise from the sharp electron density gradient created in the obscured region, and gravity waves induced by the solar eclipse process. These findings were also supported by Pal et al [2015], who deduced similar wave patterns during TSE passage through a few TRGCP.…”

Section: Solar Eclipsesupporting

confidence: 75%

On the Use of VLF Narrowband Measurements to Study the Lower Ionosphere and the Mesosphere–Lower Thermosphere

Silber

Price

2016

Surv Geophys

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The ionospheric D-region (~60 km up to ~95 km) and the corresponding neutral atmosphere, often refered to as the mesosphere-lower-thermosphere (MLT) are challenging and costly to probe in-situ. Therefore, remote sensing techniques have been developed over the years. One of these is based on VLF (Very low frequency, 3-30 kHz) electromagnetic waves generated by various natural and manmade sources. VLF waves propagate within the Earth-ionosphere waveguide, and are extremely sensitive to perturbations occurring in the D-region along their propagation path. Therefore, measurements of these signals serve as an inexpensive remote sensing technique for probing the lower ionosphere and the MLT region. This paper reviews the use of VLF narrowband (NB) signals (generated by man-made transmitters) in the study of the D-region and the MLT for over 90 years. The fields of research span time scales from microseconds to decadal variability, and incorporate lightning-induced short term perturbations; extraterrestrial radiation bursts; energetic particle precipitation events; solar eclipses; lower atmospheric waves penetrating into the D-region; sudden stratospheric warming events; the annual oscillation; the solar cycle; and finally, the potential use of VLF NB measurements as an anthropogenic climate change monitoring technique.

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Section: Solar Eclipsesupporting

confidence: 75%

On the Use of VLF Narrowband Measurements to Study the Lower Ionosphere and the Mesosphere–Lower Thermosphere

Silber

Price

2016

Surv Geophys

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“…They analyzed the derived nighttime reflection height using signals that propagated in low‐latitude regions. Besides the studies of AO and SAO, Pal et al () reported that the nighttime VLF amplitude signal also contained a 27‐day periodicity. They applied fast Fourier transform analysis to VLF signals that propagated in midlatitude and low‐latitude regions.…”

Section: Introductionmentioning

confidence: 99%

D‐Region High‐Latitude Forcing Factors

et al. 2019

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The subionospheric very low frequency (VLF) radio wave technique provides the possibility of investigating the response of the ionospheric D‐region to a diversity of transient and long‐term physical phenomena originating from above (e.g., energetic particle precipitation) and from below (e.g., atmospheric waves). In this study, we identify the periodicities that appear in VLF measurements and investigate how they may be related to changes in space weather and atmospheric activity. The powerful VLF signal transmitted from NAA (24 kHz) on the east coast of the United States, and received at Sodankylä, Finland, was analyzed. Wavelet transform, wavelet power spectrum, wavelet coherence, and cross‐wavelet spectrum were computed for daily averages of selected ionospheric, space weather, and atmospheric parameters from November 2008 until June 2018. Our results show that the significant VLF periods that appear during solar cycle 24 are the annual oscillation, semiannual oscillation, 121‐day, 86‐day, 61‐day, and solar rotation oscillations. We found that the annual oscillation corresponds to variability in mesospheric temperature and solar Lyman‐α (Ly‐α) flux and the semiannual oscillation to variability in space weather‐related parameters. The solar rotation oscillation observed in the VLF variability is mainly related to the Ly‐α flux variation at solar maximum and to geomagnetic activity variation during the declining phase of the solar cycle. Our results are important since they strengthen our understanding of the Earth's D‐region response to solar and atmospheric forcing.

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“…We apply the wavelet analysis method (Pal et al, ; Torrence & Compo, ) to the residual perturbed VLF amplitude, which has been obtained by subtracting the reference (unperturbed) signal amplitude from each day during the cyclone period, to find the signature of gravity waves. Application of wavelet analysis to the perturbed amplitude also helps to eliminate the regular variations.…”

Section: Methodsmentioning

confidence: 99%

Low‐Latitude VLF Radio Signal Disturbances Due to the Extremely Severe Cyclone Fani of May 2019 and Associated Mesospheric Response

et al. 2020

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We present new results of lower ionospheric disturbances due to the extremely severe cyclonic storm Fani over northeastern part of the Indian Ocean. Very low frequency radio signal received at Kolkata, India, and mesospheric temperature and ozone concentration data from the NASA's TIMED satellite are used for this purpose. Significant wave-like oscillations and strong amplitude anomalies in daytime and nighttime VLF signal were observed when the cyclone center was within ∼700 km from the receiver. Both the mesospheric ozone concentration and temperature showed maximum anomalies beyond 3 during the cyclone period. Maximum ozone anomaly and maximum VLF anomaly occurred on the same day when cyclone intensity was maximum, while the maximum temperature anomaly occurred on the next day during landfall. Mesospheric temperature enhancement around VLF reflection heights indicates changes in the chemical composition and electron-neutral balance in the D region ionosphere. Simulation of VLF signal showed that the D region reflection height decreased by 7.9 km and the D region electron density increased by ∼20 times compared to precyclone midnight values at the maximum perturbed area along the propagation path. Wavelet analysis confirmed significant enhancement of atmospheric gravity waves spectrum with periods 10 min to 2 hr around landfall. Further, a strong anticorrelation between total wavelet power in the wave band of periods 10-30 min and cyclone pressure suggests a possibility of monitoring cyclone intensity from mesospheric gravity waves using VLF radio measurements.

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On the use of Very Low Frequency transmitter data for remote sensing of atmospheric gravity and planetary waves

Cited by 20 publications

References 27 publications

On the Use of VLF Narrowband Measurements to Study the Lower Ionosphere and the Mesosphere–Lower Thermosphere

On the Use of VLF Narrowband Measurements to Study the Lower Ionosphere and the Mesosphere–Lower Thermosphere

D‐Region High‐Latitude Forcing Factors

Low‐Latitude VLF Radio Signal Disturbances Due to the Extremely Severe Cyclone Fani of May 2019 and Associated Mesospheric Response

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