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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 26, issue 6
Ann. Geophys., 26, 1451–1459, 2008
https://doi.org/10.5194/angeo-26-1451-2008
© Author(s) 2008. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 26, 1451–1459, 2008
https://doi.org/10.5194/angeo-26-1451-2008
© Author(s) 2008. This work is distributed under
the Creative Commons Attribution 3.0 License.

  11 Jun 2008

11 Jun 2008

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

S. Kumar, A. Kishore, and V. Ramachandran S. Kumar et al.
  • School of Engineering and Physics, The University of the South Pacific, Suva, Fiji

Abstract. Lightning generated signals recorded at a low-latitude 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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