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Equivalent electron densities at reflection heights of tweek atmospherics in the low-middle latitude D-region ionosphere


Tweek atmospherics are ELF/VLF pulse signals with frequency dispersion characteristics that originate from lightning discharges and propagate in the Earth-ionosphere waveguide mode over long distances. In this paper, we estimate equivalent nighttime electron densities at reflection heights in D-region ionosphere at low-middle latitudes by accurately reading the first-order mode cut-off frequency of tweek atmospherics. The estimation method was applied to tweek atmospherics received simultaneously at Moshiri and Kagoshima in Japan. Equivalent electron densities ranged from 20—28 el./cm3 at ionospheric reflection heights of 80—85 km. Comparing our estimates with electron density profiles obtained from the IRI-95 model, MF radar measurements, and rocket experiments revealed almost consistent results for the lower part of the D-region ionosphere. The tweek method has the unique advantage of enabling reflection-height (equivalent electron densities) monitoring over a wide area of several thousand kilometers.


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Correspondence to H. Ohya.

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Ohya, H., Nishino, M., Murayama, Y. et al. Equivalent electron densities at reflection heights of tweek atmospherics in the low-middle latitude D-region ionosphere. Earth Planet Sp 55, 627–635 (2003).

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Key words

  • Tweek atmospherics
  • cut-off frequency
  • equivalent electron densities (reflection heights)