Response of the Equatorial Ionosphere to the Annular Solar Eclipse of 15 January 2010.

This paper presents the response of the equatorial ionosphere to the noon time annular solar eclipse of 15 January 2010. The observation has been made using a Digisonde, Meteor Wind Radar, and Proton Precession Magnetometer over Trivandrum, (8.5oE; 77oN; dip lat 0.5oN), a geomagnetic dip equatorial station in India. It has been found that the E, F1, and F2 regions of the equatorial ionosphere respond to solar eclipse with different time delays, F1 being responding faster and the E and F2 regions slower. Though there have been studies on the delayed response of F2 region during the solar eclipses, the delayed response of E region is quite unexpected since this region is dominated by the recombination chemistry. The plausible reasons for this have been explored, and it is suggested that the downward diffusion of atomic oxygen plays a major role for the observed phenomenon. Key Points: This paper discusses about the altitudinally varying response of equatorial ionosphere to the annular solar eclipse of 15 January 2010It is intriguing to note that the E region electron densities were found to be responding to the solar flux changes later than those in F1 regionThe plausible reasons behind this are discussed in terms of prevailing neutral and electrodynamics and the diffusion chemistry [ABSTRACT FROM AUTHOR]