Dispersion Characteristics and Waveform Analysis of Tweek Atmospherics

Yano, Sazanami; Ogawa, T.; Hagino, H.

doi:10.1007/978-4-431-68162-5_23

Cited by 14 publications

(16 citation statements)

References 4 publications

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“…Ohtsu, 1960;Yano et al, 1989Yano et al, , 1991Hayakawa et al, 1994Hayakawa et al, , 1995Sukhorukov, 1996;Ferencz, 2004;Ferencz et al, 2007). Tweeks have been reported to be left-hand polarized (L) waves (Reznikov et al, 1993).…”

Section: Elf and Vlf Energymentioning

confidence: 99%

Higher harmonic tweek sferics observed at low latitude: estimation of VLF reflection heights and tweek propagation distance

2008

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Abstract.Lightning generated signals recorded at a lowlatitude station, Suva (18.2 • S, 178.3 • E) Fiji, in the South Pacific region, during September 2003-July 2004, are used to study the propagation features and the reflection heights of tweek atmospherics in the waveguide formed by the Earth's surface and the lower ionosphere. Tweeks are observed only during the local night and the maximum harmonic (n) recorded is six. The occurrence of tweeks with higher n progressively decreases as n increases. The dispersed part of tweeks decreases as n increases. The attenuation factor has been calculated for tweeks with n=1-3. The ionospheric reflection heights obtained assuming the transverse magnetic mode of propagation for tweek signals vary from 83-92 km. A higher harmonic of the same tweek is reflected from about 2.0 km higher than the lower harmonic. For 90% of tweeks, propagation distances are estimated to be between 1000-5000 km. Tweeks with lower n propagate longer distances than the tweeks with higher n.

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Section: Elf and Vlf Energymentioning

confidence: 99%

Higher harmonic tweek sferics observed at low latitude: estimation of VLF reflection heights and tweek propagation distance

2008

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“…General features of tweeks have been studied by several researchers [ Outsu , 1960; Yano et al , 1989; Kumar et al , 1994; Hayakawa et al , 1994, 1995; Ferencz , 2004; Ferencz et al , 2007; Kumar et al , 2008; Ohya et al , 2011]. Outsu [1960] studied dispersion characteristics of tweeks considering lower ionosphere as sharply bounded reflecting layer and the Earth as a perfectly conducting medium.…”

Section: Introductionmentioning

confidence: 99%

Morphological features of tweeks and nighttime D region ionosphere at tweek reflection height from the observations in the low‐latitude Indian sector

Maurya¹,

Singh²,

Veenadhari³

et al. 2012

J. Geophys. Res.

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, at Allahabad, a low-latitude station in the Indian sector, has been used to study seasonal occurrence which shows maximum tweek occurrence of about 63% during summer season and about 19% and 18% occurrences during equinox and winter seasons. Maximum occurrence of tweeks during summer season is consistent with the larger number of lightnings detected by World Wide Lightning Location Network in the Indian and Asia Oceania regions during summer as compared to that during equinox and winter. Seasonally, tweek (ionospheric) reflection height in the premidnight (18:00-00:00 LT) during winter is less as compared to that during equinox and summer. Annual (seasonal average) variation of the mean ionospheric reflection height shows a gradual increase in the reflection height from about 19:30 to 04:30 LT. The annual average of postmidnight (00:00-06:00 LT) reflection height is about 5 km higher as compared to that in the premidnight. Our initial results on the variability in the ionospheric reflection height under pure nighttime propagation (21:00-03:00 LT) on magnetically quiet days show a day-to-day variability of up to 8 km. Theoretically calculated attenuation of the Earth-ionosphere waveguide for first six tweek modes in the early and late night periods (21:00-00:00 LT; 00:00-03:00 LT) is less compared to that in the dusk (18:00-21:00 LT) period. The higher attenuation in the dusk period and most of the tweeks in the dawn period traveling partially under daytime conditions explain the lower occurrence of tweeks in these periods.

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“…The tweeks method for investigation of lower ionosphere has been widely used [5,[11][12][13][14][15][16][17]. Ionospheric parameters such as reflection height of tweeks, equivalent electron densities at reflection height, propagation distance and geographic locations of the source discharge have been estimated successfully using tweeks as a diagnostic tool [9,[18][19][20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Remote sensing of D-region ionosphere using multimode tweeks

et al. 2015

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Lightning discharges radiate electromagnetic waves in a wide frequency range, with maximum energy in extremely low frequency/very low frequency band. A part of the radiated extremely low frequency/very low frequency wave energy is trapped in the Earth-ionosphere waveguide and travels thousands of kilometers in different modes with lower attenuation. Amplitude, frequency and phase of these waves are used to study the less explored D-region ionosphere at lower latitudes. Extremely low frequency/very low frequency observations are recorded continuously by automatic whistler detector setup installed at low-latitude Indian station Lucknow (Geom. lat. 17.6°N; long. 154.5°E). In total, 149 cases of tweeks having modes ranging from 3 to 6 have been recorded by automatic whistler detector during December 2010 and analyzed. Result shows that the propagation distance in the Earth-ionosphere waveguide lies between 1.1 and 9.4 Mm. The electron density in the lower D-region varies between 25 and 150 cm -3 . The upper boundary of the waveguide varies between 80 and 95 km. The reported results are in good agreement with the earlier measurements at different latitudes and longitudes.

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Dispersion Characteristics and Waveform Analysis of Tweek Atmospherics

Cited by 14 publications

References 4 publications

Higher harmonic tweek sferics observed at low latitude: estimation of VLF reflection heights and tweek propagation distance

Higher harmonic tweek sferics observed at low latitude: estimation of VLF reflection heights and tweek propagation distance

Morphological features of tweeks and nighttime D region ionosphere at tweek reflection height from the observations in the low‐latitude Indian sector

Remote sensing of D-region ionosphere using multimode tweeks

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