Planetary wave oscillations in the occurrence time of Equatorial Spread-F

This paper presents the role of planetary waves in modulating the occurrence time of Equatorial Spread F (ESF). The investigation has been carried out using the data from the digital Ionosonde and Proton Precession Magnetometer located over Trivandrum, India (8.5° E; 77° N; 0.5° N dip lat.). The analysis shows that the start-time of the ESF during the winter months is modulated significantly by a planetary wave of quasi-16-day periodicity. It is suggested that these waves are propagated to ionospheric altitudes from lower atmosphere through modified electrodynamics since the equatorial electrojet and pre-reversal enhancement were also showed the same oscillations.