A case study of tidal and planetary wave coupling in the equatorial atmosphere-ionosphere system over India: preliminary results

Abstract

The present study examines the role of planetary waves and tides observed at upper mesospheric heights (~90 km) in the day-to-day variabilities of the quiet time ionospheric current system as manifested in ground magnetic field records at the dip equatorial and low latitude stations during the three month period, February–April 2008, when an experimental campaign under CAWSES-India program was conducted. The MF radars at Tirunelveli (8.7°N, 77.8°E) and Kolhapur (16.8°N, 74.2°E) provided the wind observations. The study reveals simultaneous presence of 5- to 6-day and 12- to 16-day oscillations in the radar wind fields and the strength of the equatorial electrojet (EEJ) derived from the geomagnetic field records from Tirunelveli and Alibag. Tidal winds and the amplitude of diurnal variation in the EEJ strength show a reasonably good correlation when 5-day averaged data sets are used. Though limited data were used, the present work will motivate further studies on the atmosphere – ionosphere coupling at low latitudes with extended data sets.