Possible relationship between the equatorial electrojet (EEJ) and daytime vertical E x B drift velocities in F region from ROCSAT observations

The vertical E x B drift is very important parameter as its day to day variability has great influence on the variability in the low latitude F-region ion and electron density distributions. The measurements of vertical ion velocity from the first Republic of China Satellite (ROCSAT-1) provide a unique data base for the development of possible relationship between vertical E x B drifts and ground based magnetometer observation. An attempt has been made to derive quantitative relationship between F-region vertical E x B drifts measured by ROCSAT-1 (600 km) and ground measured equatorial electrojet for the solar maximum period 2001-2003 for Indian and Japanese sectors. The results consistently indicate existence of linear relationship between the measured vertical E x B drifts at topside F-region and EEJ for both the sectors, with a moderate to high correlation coefficients. The linear relationship between ROCSAT-1 measured E x B drifts and EEJ for Indian and Japanese sectors has been compared with a similar relationship with Jicamarca Unattended Long-term Ionosphere Atmosphere Radar (JULIA) measured E x B drifts (150 km echos) and EEJ strength from Peruvian sector during 2003. It has been found that ROCSAT-1 measured E x B drifts shows linear relationship with EEJ, however, exhibits a larger scatter unlike JULIA radar observed E x B drifts. This may be attributed to the large height difference as ROCSAT-1 measures E x B drifts at 600 km altitude and the EEJ is E-region (110 km) phenomenon. (C) 2016 COSPAR. Published by Elsevier Ltd. All rights reserved.