Annales Geophysicae ISSN: 0992-7689 (printed version) ISSN: 1432-0576 (electronic version) Abstract Volume 13 Issue 8 (1995) pp 871-878
Equatorial night-time F-region zonal electric fields S. S. Hari, B. V. Krishna Murthy Space Physics Laboratory, Vikram Sarabhai Space Centre, Trivandrum 695022, India Received: 18 July 1994/Revised: 6 December 1994/Accepted: 16 January 1995 Abstract. Night-time F-region vertical electrodynamic drifts at the magnetic equatorial station, Trivandrum are obtained for a period of 2 years, 1989 and 1990 (corresponding to solar cycle maximum epoch), using ionosonde h'F data. The seasonal variation of the vertical drift is found to be associated with the longitudinal gradients of the thermospheric zonal wind. Further, the seasonal variation of the prereversal enhancement of the vertical drift is associated with the time difference between the sunset times of the conjugate E-regions (magnetic field line linked to F-region) which is indicative of the longitudinal gradients of the conductivity (of the E-region). The vertical drifts and the causative zonal electric fields at Trivandrum are compared with those at Jicamarca and F-region zonal electric field models. It is seen that the night-time downward drift (as also the causative westward electric field) at Jicamarca is greater than that at Trivandrum. The prereversal enhancement of the drift is greater at Jicamarca than at Trivandrum during the summer and the equinoxes, whereas during the winter the opposite is the case. Article not available online Last change: October 3, 1997
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