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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 27, issue 1
Ann. Geophys., 27, 107–111, 2009
https://doi.org/10.5194/angeo-27-107-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 27, 107–111, 2009
https://doi.org/10.5194/angeo-27-107-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.

  06 Jan 2009

06 Jan 2009

Electrodynamics of the equatorial F-region ionosphere during pre-sunrise period

S. R. Prabhakaran Nayar1, T. J. Mathew1, C. V. Sreehari1, S. G. Sumod1, C. V. Devasia2, S. Ravindran2, V. Sreeja2, T. Kumar Pant2, and R. Sridharan2 S. R. Prabhakaran Nayar et al.
  • 1Department of Physics, University of Kerala, Kariavattom, Trivandrum, 695 581, India
  • 2Space Physics Laboratory, Vikram Sarabhai Space Centre, Trivandrum 695 022, India

Abstract. The electrodynamics of the pre-sunrise equatorial F-region is investigated using HF Doppler radar and digital ionosonde. The observations are limited to those days for which the radar probing frequency is below the foF2 value. The ionosphere observation using HF Doppler radar exhibit interesting features during pre-sunrise period similar to the post sunset pre-reversal enhancement. The most striking feature observed during pre-sunrise period is the sudden downward excursion in the vertical drift around local sunrise followed by an upward turning. Pre-sunrise observations of vertical plasma drift and the sunrise downward excursion followed by an upward turning after the ground sunrise related to the zonal electric field at the equatorial F-region are the most significant results not reported earlier.

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