A study of spatio-temporal variability of equatorial electrojet using long-term ground-observations

Abstract

It is widely accepted that a quiet time equatorial electrojet (EEJ) varies daily, monthly, seasonally, and longitudinally; however, detailed characterization of these variations has not yet been done using multiple ground based stations. Therefore, the purpose of this article is to give a reasonably comprehensive comparison of day-to-day, monthly, seasonal, and longitudinal variabilities of the EEJ and its reversal counter electrojet (CEJ) occurrence during the period from 2011 to 2013. The analysis is based on a 1-minute ground-based magnetic data recorded at eight dip equatorial stations. The results obtained in this study indicate that the mean day-side EEJ is strongest around equinoxes months in the Peruvian, Southeast Asia and Philippine regions throughout the years investigated. On the other hand, stations in the African and Indian regions show medium peaks in the equinoxes months of the years 2011–2012. The EEJ strength in the Pacific sector is weakest throughout the years. The observed seasonal behavior of the peak EEJ during equinox is observed at 10:30–12:00 LT for Peruvian, Southeast Asian, and Philippine regions, but in the West African and Indian sectors, the medium EEJ peaks were observed about 1 h earlier. We also found that, on average, morning CEJ events occur more frequently than in the evening CEJ at TTB followed by AAE and HUA. The largest morning CEJ fluctuations were observed for the TTB during the whole months of the years considered in this study except the December months of 2012. During the December solstice months of 2011, the EEJ current in TTB is maximum while the medium peak has been shown in 2012 and 2013. Overall the observed average EEJ strength is maximum during equinoxes and minimum in solstices months as well as seasons. Our results also show that the magnitude of EEJ gradually increases in the Peruvian and Southeast Asian sectors while the rate of MCEJ occurrence increases at Brazilian and African regions from the years 2011 to 2013. It is also observed that the magnitude of EEJ is highering during the years of the increasing solar cycle.