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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.


  1. Bickel, J. E., J. A. Ferguson, and G. V. Stanley, Experimental observation of magnetic field effects on VLF propagation at night, Radio Science, 5, 19, 1970.

  2. Budden, K. G., Radio Waves in the Ionosphere, Cambridge University Press, 1961.

  3. Hayakawa, M., K. Ohta, and K. Baba, Wave characteristics of tweek atmospherics deduced from the direction-finding measurement and theoretical interpretation, J. Geophys. Res., 99, 10733–10743, 1994.

  4. Holdsworth, D. A., R. Vuthaluru, I. M. Reid, and R. A. Vincent, Differential absorption measurements of mesospheric and lower thermospheric electron densities using the Buckland Park MF radar, J. Atmos. Sol.-Terr. Phys., 64, 2029–2042, 2002.

  5. Igarashi, K., Y. Murayama, M. Nagayama, and S. Kawana, D-region electron density measurements by MF radar in the middle and high latitudes, Adv. Space Res., 25, 25–32, 2000. Maeda, K-i., Study on electron density profile in the lower ionosphere, J. Geomag. Geoelectr., 23, 133–159, 1971.

  6. Nagano, I. and T. Okada, Electron density profiles in the ionospheric D-region estimated from MF radio wave absorption, Adv. Space Res., 25, 33–42, 2000.

  7. Nishino, M. and M. Kashiwagi, The characteristics of the distribution of atmospherics and the consideration of the fixing error, Proc. Res. Inst. Atmos., Nagoya University, 23, 1–16, 1976.

  8. Outsu, J., Numerical study of tweeks based on waveguide mode theory, Proc. Res. Inst. Atmos., Nagoya University, 7, 58–71, 1960.

  9. Ryabov, B. S., Tweek propagation peculiarities in the Earth-ionosphere waveguide and low ionosphere parameters, Adv. Space Res., 12(6), (6)255–(6)258, 1992.

  10. Shimakura, S., M. Moriizumi, and M. Hayakawa, On the observation of the ionospheric disturbances based on dispersion property of atmospherics propagation in the Earth-ionosphere waveguide, The IEICE Transactions on Communications (Japanese Edition), A.P90 -17, 27—33, 1990 (in Japanese).

  11. Shvets, A. V. and M. Hayakawa, Polarization effects for tweek propagation, J. Atmos. Sol.-Terr. Phys., 60(4), 461–469, 1998.

  12. Thomas, L. and M. D. Harrison, The electron density distributions in the D-region during the night and pre-sunrise period, J. Atmos. Terr. Phys., 55, 173, 1970.

  13. Thomson, N. R., Experimental daytime VLF ionospheric parameters, J. Atmos. Terr. Phys., 55, 173, 1993.

  14. Wait, J. R., Electromagnetic Waves in Stratified Media, Pergamon Press, 147, 1970.

  15. Yamashita, M., Propagation of tweek atmospherics, J. Atmos. Terr. Phys., 40, 151, 1978.

  16. Yano, S., T. Ogawa, and H. Hagino, Waveform analysis of tweek atmospherics, Research Letter of Atmosheric Electricity, 9, 31–42, 1989.

  17. Yedemsky, D., B. S. Ryabov, A. Shchokotov, and V. S. Yarotsky, Experimental investigation of the tweek field structure, Adv. Space Res., 12, 251–254, 1992.

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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)