Skip to main content
Earth, Planets and Space
Download PDF

The seasonal and solar cycle variations of electron density gradient scale length, vertical drift and layer height during magnetically quiet days: Implications for Spread F over Trivandrum, India

Earth, Planets and Space volume 61, pages 1339–1343 (2009)Cite this article

Abstract

A study has been carried out on the behaviour of electron density gradient scale length, L, vertical drift and layer height, around post sunset hours, during the magnetically quiet days of summer, winter and equinox seasons of solar maximum (2002) and minimum years (1995), using ionosonde data of Trivandrum (8.5°N, 76.5°E, dip = 0.5°N) in the Indian longitude sector. The results indicate a clear seasonal and solar cycle variation in all the three parameters. Further, the seasonal variation of equatorial Spread F (ESF) during the above period is examined in terms of the relative roles of L, the vertical drift and layer height (of the F layer) in the triggering of the collisional Rayleigh-Taylor instability. The results, show for the first time, that L also plays an important role, in controlling the quiet time seasonal and solar cycle variability of ESF; whereas in earlier studies this parameter had been taken to be constant. The detailed results are presented and discussed.

References

  • Abdu, M. A., I. S. Batista, and J. A. Bittencourt, Some characteristics of Spread F at the magnetic equatorial station Fortaleza, J. Geophys. Res., 86(A8), 6836–6842, 1981.

    Article  Google Scholar 

  • Chandra, H. and R. G. Rastogi, Solar cycle and seasonal variation of Spread F near the magnetic equator, J. Atmos. Sol. Terr. Phys., 32, 439–444, 1970.

    Article  Google Scholar 

  • Devasia, C. V., N. Jyoti, K. S. Viswanathan, K. S. V. Subbarao, D. Tiwari, and R. Sridharan, On the plausible linkage of thermospheric meridional winds with equatorial Spread F, J. Atmos. Sol. Terr. Phys., 64, 1–12, 2002.

    Article  Google Scholar 

  • Farley, D. T., B. B. Balsley, R. F. Woodman, and J. P. McClure, Equatorial Spread F: Implications of VHF radar observations, J. Geophys. Res., 75, 7199–7216, 1970.

    Article  Google Scholar 

  • Fejer, B. G. and M. C. Kelley, Ionospheric irregularities, Rev. Geophys Space Phys., 18, 401–454, 1980.

    Article  Google Scholar 

  • Fejer, B. G., L. Scheerliess, 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, 19859–19869, 1999.

    Article  Google Scholar 

  • Fuller-Rowell, T. J., M. V. Codrescu, R. J. Moffett, and S. Quegan, On the seasonal response of the thermosphere and ionosphere to geomagnetic storms, J. Geophys. Res., 101, 2343–2353, 1996.

    Article  Google Scholar 

  • Haerendel, G., Theory of equatorial Spread F, Report, Max-Plank inst. fur Phys. and Astrophys., Munich, 1973.

    Google Scholar 

  • Hysell, D. L. and J. Burcham, Long term studies of equatorial spread F using the JULIA radar at Jicamarca, J. Atmos. Terr. Phys., 64, 1531–1543, 2002.

    Article  Google Scholar 

  • Jyoti, N., C. V. Devasia, R. Sridharan, and D. Tiwari, Threshold height (h’Fc) for the meridional wind to play a deterministic role in the bottom side equatorial Spread F and its dependence on solar activity, Geophys. Res. Lett., 31, L12809, doi:10.1029/2004GL019455, 2004.

  • Kelley, M. C. and J. P. McClure, Equatorial Spread-F: a review of recent experimental results, J. Atmos. Terr. Phys., 43, 427–435, 1981.

    Article  Google Scholar 

  • Krishna Murthy, B. V., S. S. Hari, and V. V. Somayajulu, Nighttime equatorial thermospheric meridional winds from h’F data, J. Geophys. Res., 95, 4307–4310, 1990.

    Article  Google Scholar 

  • Manju, G., C. V. Devasia, and R. Sridharan, On the seasonal varations of the threshold height for the occurrence of equatorial Spread F during solar minimum and maximum years, Ann. Geophys., 25, 1, 2007.

    Article  Google Scholar 

  • Manju, G., C. V. Devasia, and S. Ravindran, The seasonal and solar cycle variations of electron density gradient scale length during magnetically disturbed days: implications for Spread F, Earth Planets Space, 61, 913–917, 2009.

    Article  Google Scholar 

  • Maruyama, T. and N. Matuura, Longitudinal variability of annual changes in activity of ESF and plasma depletions, J. Geophys. Res., 89, 10903–109012, 1984.

    Article  Google Scholar 

  • Sekar, R. and R. Raghavarao, Role of vertical winds on the Rayleigh- Taylor instabilities of the nighttime equatorial ionosphere, J. Atmos. Terr. Phys., 49, 981–985, 1987.

    Article  Google Scholar 

  • Subbarao, K. S. V. and B. V. Krishna Murthy, Seasonal variations of equatorial Spread F., Ann. Geophys., 12, 33–39, 1994.

    Google Scholar 

  • Tulasi Ram, S., P. V. S. Rama Rao, K. Niranjan, D. S. V. V. D. Prasad, R. Sridharan, C. V. Devasia, and Sudha Ravindran, The role of post-sunset vertical drifts in predicting the onset of VHF scintillations during high and low sunspot activity, Ann. Geophys., 24, 1609–1616, 2006.

    Article  Google Scholar 

  • Whitehead, J., Ionization disturbances caused by gravity waves in the presence of an electrostatic field and background wind, J. Geophys. Res., 76, 238–241, 1971.

    Article  Google Scholar 

  • Woodman, R. F. and C. LaHoz, Radar observations of F region equatorial irregularities, J. Geophys. Res., 81, 5447–5466, 1976.

    Article  Google Scholar 

Download references

Author information

Authors and Affiliations

  1. Vikram Sarabhai Space Centre, Space Physics Laboratory, 695 022, Trivandrum, Kerala, India

    G. Manju, C. V. Devasia & Sudha Ravindran

Authors
  1. G. Manju
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. C. V. Devasia
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Sudha Ravindran
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to G. Manju.

Rights and permissions

Open Access  This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made.

The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.

To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/.

Reprints and Permissions

About this article

Cite this article

Manju, G., Devasia, C.V. & Ravindran, S. The seasonal and solar cycle variations of electron density gradient scale length, vertical drift and layer height during magnetically quiet days: Implications for Spread F over Trivandrum, India. Earth Planet Sp 61, 1339–1343 (2009). https://doi.org/10.1186/BF03352986

Download citation

  • Received:

  • Revised:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1186/BF03352986

Key words

  • Equatorial ionosphere
  • ionospheric irregularities
  • plasma instability
  • equatorial Spread F