On the variability of the Equatorial Ionization Anomaly Trough over Indian region: A novel analysis using Beacon TEC measurements

Abstract

A novel method using single station beacon Relative Slant Total Electron Content (RSTEC) measurements is proposed to estimate the location of Equatorial Ionization Anomaly Trough (EAT). The feasibility of this method is established based on simulations of RSTEC using (International Reference Ionosphere) IRI model electron densities.Using the RSTEC measured by the Coherent Radio Beacon Receiver at Thiruvananthapuram (8.5° N geographic North, 77° geographic E, 0.5° N dip north), the spatial variability of the EAT location during 2006–2007 over the Indian region has been analyzed. The differential phase of signals emitted by beacons at 150 MHz and 400 MHz on board low earth orbiting satellites (LEOS) has been used to estimate the RSTEC. This study shows that EAT exhibits local time (morning – afternoon) variation as large as 7 degrees on either side of the dip equator. Further the trough location exhibits a systematic latitudinal change with seasons. The combined control of trans-hemispheric winds as well as magnetic field aligned diffusion is found to be the reason for the observed properties of trough location.