The Lower Ionospheric VLF/LF Response to the 2017 Great American Solar Eclipse Observed Across the Continent

Cohen, M. B.; Gross, N. C.; Higginson‐Rollins, M. A.; Marshall, R. A.; Gołkowski, Mark; Liles, William; Rodríguez, Daniel; Rockway, J. W.

doi:10.1002/2018gl077351

Cited by 27 publications

(19 citation statements)

References 25 publications

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“…We found that for all three paths there was no noticeable influence on amplitude; however, the phase revealed a significant decrease during the eclipse. For the two signals transmitted from NPM and NML transmitters which both had frequencies close to 20 kHz the negative phase anomalies were −33° and −35°, correspondingly, which is in good agreement with the experimental results, obtained by Cohen et al () and Moore and Burch () for the American paths. Note that the anomalies lasted longer for the longer path.…”

Section: Discussionsupporting

confidence: 91%

“…In the current work we use phase and amplitude observations of sub‐ionospheric VLF/LF signals to analyze the response of the lower ionosphere to the Great American Eclipse on 21 August 2017. This eclipse has been analyzed in detail by Cohen et al () using observations from 11 VLF/LF receivers across the continental United States. Results of the analysis have shown increase in amplitude up to 5 dB during eclipse together with decrease in phase ≈10−50°.…”

Section: Introductionmentioning

confidence: 99%

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The Effect of the 21 August 2017 Total Solar Eclipse on the Phase of VLF/LF Signals

Рожной

Solovieva

Шалимов

et al. 2020

Earth and Space Science

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An experimental study of the phase and amplitude observations of sub‐ionospheric very low and low frequency (VLF/LF) signals is performed to analyze the response of the lower ionosphere during the 21 August 2017 total solar eclipse in the United States of America. Three different sub‐ionospheric wave paths are investigated. The length of the paths varies from 2,200 to 6,400 km, and the signal frequencies are 21.4, 25.2, and 40.75 kHz. The two paths cross the region of the total eclipse, and the third path is in the region of 40–60% of obscuration. None of the signals reveal any noticeable amplitude changes during the eclipse, while negative phase anomalies (from −33° to −95°) are detected for all three paths. It is shown that the effective reflection height of the ionosphere in low and middle latitudes is increased by about 3–5 km during the eclipse. Estimation of the electron density change in the lower ionosphere caused by the eclipse, using linear recombination law, shows that the average decrease is by 2.1 to 4.5 times.

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Section: Discussionsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

The Effect of the 21 August 2017 Total Solar Eclipse on the Phase of VLF/LF Signals

Рожной

Solovieva

Шалимов

et al. 2020

Earth and Space Science

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show abstract

“…Only one VLF observation location was employed, however, and the effect of the solar flare was not readily discernible in the data, which had to be interpreted in the context of a model. Cohen et al () report VLF observations of the August 2018 eclipse but focus their analysis on the polarization of the VLF signals and conclude that the solar flare considered here did not significantly impact their measurements. It is thus the case that simultaneous multisite observations of the lunar occultation of a solar flare have not previously been reported.…”

Section: Introductionmentioning

confidence: 98%

The D Region Response to the August 2017 Total Solar Eclipse and Coincident Solar Flare

Moore

Burch

2018

Geophysical Research Letters

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During the solar eclipse of 21 August 2017, the University of Florida monitored very low frequency (3–30 kHz) radio activity at ten locations, enabling the remote sensing of the D region ionosphere (∼50‐ to 100‐km altitude). Two of the locations were far enough away (Antarctica) that no response to the eclipse was detected despite the fact that the eclipse significantly shadowed the transmitter. A particularly rare observation is presented: Three receivers were at locations where the Moon blocked at least some of the solar X‐ray flare that occurred near 1800 UT, providing high‐resolution observations of solar flare occultation by the Moon. The remainder of the sites registered meaningful responses to both the solar eclipse and the solar flare. Observations indicate that very low frequency signal propagation is affected once 30–55% obscuration is achieved anywhere along the propagation path. No long‐term or delayed effects, such as atmospheric gravity waves, were observed.

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“…VLF/LF signals propagate over long distances in the Earth‐ionosphere waveguide with low attenuation and can be picked up by a receiver at ground. These signals sample the properties of the continuously changing D region ionosphere along the propagation path and therefore can be used to study various ionospheric phenomena, such as gamma‐ray bursts (Fishman & Inan, ; Mondal et al, ), solar flares (Palit et al, ; Thomson & Clilverd, ), solar eclipses (Clilverd et al, ; Cohen et al, ; Pal et al, ), geomagnetic disturbances (Tatsuta et al, ), and references therein.…”

Section: Introductionmentioning

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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The Lower Ionospheric VLF/LF Response to the 2017 Great American Solar Eclipse Observed Across the Continent

Cited by 27 publications

References 25 publications

The Effect of the 21 August 2017 Total Solar Eclipse on the Phase of VLF/LF Signals

The Effect of the 21 August 2017 Total Solar Eclipse on the Phase of VLF/LF Signals

The D Region Response to the August 2017 Total Solar Eclipse and Coincident Solar Flare

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

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