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Quantitative estimates of relationships between geomagnetic activity and equatorial spread-F as determined by TID occurrence levels

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Using a world-wide set of stations for 15 years, quantitative estimates of changes to equatorial spread-F (ESF) occurrence rates obtained from ionogram scalings, have been determined for a range of geomagnetic activity (GA) levels, as well as for four different levels of solar activity. Average occurrence rates were used as a reference. The percentage changes vary significantly depending on these subdivisions. For example for very high GA the inverse association is recorded by a change of −33% for Rz ≥ 150, and −10% for Rz < 50. Using data for 9 years for the equatorial station, Huancayo, these measurements of ESF, which indicate the presence of TIDs, have also been investigated by somewhat similar analyses. Additional parameters were used which involved the local times of GA, with the ESF being examined separately for occurrence pre-midnight (PM) and after-midnight (AM). Again the negative changes were most pronounced for high GA in Rz-max years (−21%). This result is for PM ESF for GA at a local time of 1700. There were increased ESF levels (+31%) for AM ESF in Rz-min years for high GA around 2300 LT. This additional knowledge of the influence of GA on ESF occurrence involving not only percentage changes, but these values for a range of parameter levels, may be useful if ever short-term forecasts are needed. There is some discussion on comparisons which can be made between ESF results obtained by coherent scatter from incoherent-scatter equipment and those obtained by ionosondes.


  1. Argo, P. E., M. C. Kelley, Digital ionosonde observations during equatorial spread-F, J. Geophys. Res., 91, 5539–5555, 1986.

  2. Bowman, G. G., Further studies of “spread-F” at Brisbane—I., experimental, Planet. Space Sci., 2, 133–149, 1960.

  3. Bowman, G. G., A review of some recent work on mid-latitude spread-F occurrence as detected by ionosondes, J. Geomag. Geoelectr., 42, 109–138, 1990.

  4. Bowman, G. G., Nighttime mid-latitude travelling ionospheric disturbances associated with mild spread-F conditions, J. Geomag. Geoelectr., 43, 899–920, 1991a.

  5. Bowman, G. G., Ionospheric frequency spread and its relationship with range spread in mid-latitude regions, J. Geophys. Res., 96, 9745–9753, 1991b.

  6. Bowman, G. G., The influence of the upper-atmosphere neutral particle density on the occurrence of equatorial spread-F, Ann. Geophys., 11, 624–633, 1993a.

  7. Bowman, G. G., Daytime and nighttime mid-latitude ionospheric disturbances and their delayed occurrence after geomagnetic activity, Indian J. Radio Space Phys., 22, 1–10, 1993b.

  8. Bowman, G. G., Short-term delays in the occurrence of mid-latitude ionospheric disturbances following other geophysical and solar events, J. Geomag. Geoelectr., 46, 297–309, 1994.

  9. Bowman, G. G., Multiplicity of travelling disturbances in the nighttime mid-latitude F2-region ionosphere, Indian J. Radio Space Phys., 24, 91–96, 1995a.

  10. Bowman, G. G., Short-term delays in ionogram-recorded equatorial spread-F occurrence after both solar and geomagnetic activity, Ann. Geophys., 13, 1331–1342, 1995b.

  11. Bowman, G. G., Short term delays (hours) of ionospheric spread-F occurrence, at a range of latitudes, following geomagnetic activity, J. Geophys. Res., 103, 11,627–11,634, 1998.

  12. Croxton, F. E., Tables of Areas in Two Tails and One Tail of the Normal Curve, Prentice-Hall, Inc., London, 1949.

  13. Deminova, G. F., V. M. Shashunkina, and E. E. Goncharova, A global empirical model of effects of large-scale internal gravity waves in the night-time ionosphere, J. Atmos. Solar-Terr. Phys., 60, 227–245, 1998.

  14. Fejer, B. G., L. Scherliess, Empirical models of storm time equatorial zonal electric fields, J. Geophys. Res., 102, 24,047–24,056, 1997.

  15. Fejer, B. G., L. Scherliess, and E. R. de Paula, Effects of the vertical plasma drift velocity on the generation and evolution of equatorial spread F, J. Geophys. Res., 104, 19,859–19,869, 1999.

  16. Flaherty, J. P., M. C. Kelley, C. E. Seyler, and T. J. Fitzgerald, Simultaneous VHF and transequatorial HF observations in the presence of bottomside equatorial spread F, J. Geophys. Res., 101, 26,811–26,818, 1996.

  17. Hajkowicz, L. A., Monitoring ionospheric response to auroral electrojet activity from sub-auroral to equatorial latitudes in the east Asian-Australian longitudinal sector over a solar cycle (1978–1986), J. Atmos. Solar-Terr. Phys., 61, 857–866, 1999.

  18. Hysell, D. L., M. C. Kelley, W. E. Swartz, and R. F. Woodman, Seeding and layering of equatorial spread F by gravity waves, J. Geophys. Res., 95, 17,253–17,260, 1990.

  19. Kelley, M. C., The Earth’s Ionosphere, Academic, San Diego, Calif., 1989.

  20. Kelley, M. C. and D. L. Hysell, Equatorial spread-F and neutral atmospheric turbulence: a review and a comparative anatomy, J. Atmos. Terr. Phys., 53, 695–708, 1991.

  21. Kelley, M. C., M. F. Larson, and C. LaHoz, Gravity wave initiation of equatorial spread F; A cade study, J. Geophys. Res., 86, 9087–9100, 1981.

  22. Rastogi, R. G., On the occurrence of equatorial spread-F in the evening hours, J. Atmos. Terr. Phys., 48, 687–693, 1986.

  23. Rostoker, G., A quantitative relationship between AE and KP, J. Geophys. Res., 96, 5853–5857, 1991.

  24. Rottger, J., Wavelike structures of large scale equatorial spread F irregularities, J. Atmos. Terr. Phys., 35, 1195–1206, 1973.

  25. Sales, G. S., B. W. Reinisch, J. L. Scali, and C. Dozois, Spread F and the structure of equatorial ionization depletions in the southern anomaly region, J. Geophys. Res., 101, 26,819–26,827, 1996.

  26. Sastri, J. H., Post-midnight onset of spread-F at Kodaikanal during the June solstice of solar minimum, Ann. Geophys., 17, 1111–1115, 1999.

  27. Scherliess, L. and B. G. Fejer, Storm time dependence of equatorial disturbance dynamo zonal electric fields, J. Geophys.Res., 102, 24,037–24,046, 1997.

  28. Singh, S., D. K. Bamgboye, J. P. McClure, and F. S. Johnson, Morphology of equatorial plasma bubbles, J. Geophys.Res., 102, 20,019–20,029, 1997a.

  29. Singh, S., F. S. Johnson, and R. A. Power, Gravity wave seeding of equatorial plasma bubbles, J. Geophys. Res., 102, 8399–7410, 1997b.

  30. Subbarao, K. S. V. and B. V. Krishna Murthy, Post-sunset F-region vertical velocity variations at magnetic equator, J. Atmos. Terr. Phys., 56, 59–65, 1994.

  31. Weber, E. J., S. Basu, T. W. Bullett, C. Valladares, G. Bishop, K. Groves, H. Kuenzler, P. Ning, P. J. Sultan, R. E. Sheehan, and J. Araya, Equatorial plasma depletion precursor signatures and onset observed at 11°south of the magnetic equator, J. Geophys. Res., 101, 26,829–26,838, 1996.

  32. Wright, J. W., P. E. Argo, and M. L. V. Pitteway, On the radiophysics and geophysics of ionogram spread F, Radio Sci., 31, 349–366, 1996.

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Bowman, G.G., Mortimer, I.K. Quantitative estimates of relationships between geomagnetic activity and equatorial spread-F as determined by TID occurrence levels. Earth Planet Sp 52, 451–458 (2000) doi:10.1186/BF03352257

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  • Geomagnetic Activity
  • Universal Time
  • Ionospheric Disturbance
  • Rayleigh Taylor Instability
  • Coherent Scatter