Abstract
Abstract. While the formation of equatorial electrojet (EEJ) and its temporal variation is believed to be fairly well understood, the longitudinal variability at all local times is still unknown. This paper presents a case and statistical study of the longitudinal variability of dayside EEJ for all local times using ground-based observations. We found EEJ is stronger in the west American sector and decreases from west to east longitudinal sectors. We also confirm the presence of significant longitudinal difference in the dusk sector pre-reversal drift, using the ion velocity meter (IVM) instrument onboard the C/NOFS satellite, with stronger pre-reversal drift in the west American sector compared to the African sector. Previous satellite observations have shown that the African sector is home to stronger and year-round ionospheric bubbles/irregularities compared to the American and Asian sectors. This study's results raises the question if the vertical drift, which is believed to be the main cause for the enhancement of Rayleigh–Taylor (RT) instability growth rate, is stronger in the American sector and weaker in the African sector – why are the occurrence and amplitude of equatorial irregularities stronger in the African sector?
Highlights
The worldwide solar-driven wind results in the so-called Sq current system in the E region of the earth’s ionosphere (100–130 km altitude)
The situation of the ground-based instruments improved considerably after the launch of a United Nations sponsored program known as the International Space Weather Initiative (ISWI), a continuation of the International Heliophysical Year (IHY), which has facilitated the deployment of a number of small instrument arrays, including magnetometers (Yizengaw et al, 2013a)
In this study we used pairs of magnetometers located at different longitudes and investigated the longitudinal/seasonal variability of the EEJ intensity and the vertical E × B drift magnitude and direction
Summary
The worldwide solar-driven wind results in the so-called Sq (solar quiet) current system in the E region of the earth’s ionosphere (100–130 km altitude). The launch of different LEO satellites with magnetometers onboard, such as Ørsted, Challenging Minisatellite Payload (CHAMP), and Scientific Application SatelliteC (SAC-C), provide the opportunity to image the longitudinal EEJ distribution which shows some common features Both Ørsted (e.g., Ivers et al, 2003) and CHAMP (e.g., Luhr et al, 2004) observations show clear dependence on longitude, with stronger EEJ intensity peaks over South America and Indonesia, which they attributed to the dependence of the Cowling conductivity on the ambient field strength. The situation of the ground-based instruments improved considerably after the launch of a United Nations sponsored program known as the International Space Weather Initiative (ISWI), a continuation of the International Heliophysical Year (IHY), which has facilitated the deployment of a number of small instrument arrays, including magnetometers (Yizengaw et al, 2013a) These arrays of instruments allow us to partially cover the largest landmass beneath the geomagnetic equator, especially in regions that had been devoid of ground-based instruments, such as in Africa. Data from an ion velocity meter (IVM) instrument onboard the Communications/Navigation Outage Forecasting System (C/NOFS) satellite have been used to perform the longitudinal variation of in situ drift velocity
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
