Articles | Volume 27, issue 1
https://doi.org/10.5194/angeo-27-107-2009
https://doi.org/10.5194/angeo-27-107-2009
06 Jan 2009
 | 06 Jan 2009

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

S. R. Prabhakaran Nayar, T. J. Mathew, C. V. Sreehari, S. G. Sumod, C. V. Devasia, S. Ravindran, V. Sreeja, T. Kumar Pant, and R. Sridharan

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.