Characterization of the equatorial electrojet and its magnetic signatures deduced from Swarm observations

Abstract

This paper presents a long-term comprehensive analysis of the Equatorial Electrojet (EEJ) and Counter Equatorial Electrojet (CEJ) from the Absolute Scalar Magnetometers (ASM) on the Swarm satellites, for the period of nine years (2014–2022). For the first time, the altitude-dependent characteristics of the CEJ and EEJ have been determined, and the influence of the disturbance dynamo electric field (DDEF) and prompt penetration electric field (PPEF) on CEJ occurrence rates, EEJ and Equatorial electric field (EEF) amplitudes has been investigated. Results reveal that the DDEF was more pronounced in the morning sector (07:00–12:00 LT), while an eastward PPEF was dominant in the afternoon sector (12:00–18:00 LT). The strongest EEJ magnetic signals are observed during September equinox months, while the weakest EEJ signals occur during the June solstice months. Additionally, the EEJ increases with solar activity but appears reduced from Swarm B. The gradient of the EEJ is positive from 06:00 to 10:00 LT and negative from 11:00 to 17:00 LT, with the peak value around 08:00 LT. The largest EEJ gradients are observed in January, and the smallest gradients in March. The EEJ lunar tidal modulation is greatest in December and least in June. The CEJ occurrence rates from Swarm A, B, and C exhibited a consistent pattern of lunar tidal modulation.