Abstract
Background/ Objective: University of Kerala, Thiruvananthapuram ( 8.5◦N ,77◦E, dip 0.5◦N ) in India had a lively Space Physics research group since 1982, owing to proximity of the location to the geomagnetic dip equator. In 1982, a single frequency HF Doppler radar, operational at 5.5 MHz was installed in the University which provided many invaluable scientific results regarding the night time ionospheric F region. In 2003, it was upgraded to a new multifrequency HF Doppler Radar thereby enabling detailed examination of vertical plasma drift measurements at three different altitudes of F-region, in a nearsimultaneous manner. Methods: This study is basically a brief review of major results of F –region electrodynamics over Indian longitudinal sector obtained exclusively using HF Radar data. Findings: This review brings all the scientific results obtained using HF Radar about vertical drift studies over equatorial latitude and found that nearly about 40 research papers have been published in reputed national and international journals using the Radar data. Novelty: In a complementary point of view, this gives an opportunity to revisit and remember the important contributions of many of the earlier Indian scientists, who enriched ionospheric science using this unique facility. Keywords: HF Doppler Radar; Ionosphere; Vertical drift
Highlights
As is well-known, the ionosphere is a dynamical system having different layers and exhibits various types of plasma motions
Other than the primary observation of day to day variation in vertical plasma drift (Vd), they carried out the studies regarding the seasonal variation of Pre-Reversal Enhancement (PRE) in Zonal electric field using a sounding frequency of 3.5 MHz
They could see that as the season advances from summer to equinox, the magnitude of Vd increases and again from equinox to winter Vd decreases for 70 days of observation
Summary
As is well-known, the ionosphere is a dynamical system having different layers and exhibits various types of plasma motions. In the year 1982, HF Doppler radar was developed in the University[6] under the ISRO RESPOND programme and operated with support from University Grants Commission (UGC) This was primarily intended for the studies of F region dynamics with emphasis on Pre-Reversal Enhancement (PRE) during the post sunset period. This radar was operated in the spaced-receiver configuration mode, and could determine velocity vector of the plasma drift. Only a vertical sounding facility was installed with one transmitting and one receiving antenna .Two more antennas - one for zonal and another for meridional drift measurements were installed in the second phase during 2006 Both single frequency and multi frequency provided invaluable information about the plasma drifts of the ionosphere during pre sunrise and post sunset periods. The following sections provide the technical details of single and multifrequency radar, method of evaluation of plasma drift and the important scientific contributions came out using the HF Doppler Radar over equatorial region of Thiruvananthapuram in the Indian longitudinal sector
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