The Short‐Periodic Response of Equatorial Electrojet to the Temporal Variations of IMF Bz During Geomagnetic Quiet Time.

The equatorial electrojet (EEJ) is an important and intense ionospheric current, flowing in a narrow band along the dip equator. Using the total electron content from Global Navigation Satellite System, electron density from Swarm, EEJ from Tatuoca station, and the corresponding Thermosphere‐Ionosphere Electrodynamic General Circulation Model simulations, this work investigates the behaviors of quiet‐time EEJ during the temporal oscillations of interplanetary magnetic field (IMF) Bz. It is found that an average relative perturbation of 17.5%, 5.51% and 23.17% could be generated in the quiet time EEJ on August 24 in 2021, 2022, and 2023, respectively. The prominent feature shown in EEJ changes is the short‐periodic oscillations with high frequency and a period of tens of minutes. A power spectrum from wavelet supports that the small‐scale perturbations with high frequency are mainly attributed to the prompt penetration electric field (PPEF). During the temporal oscillations of IMF Bz, a similar spectrum is established between IMF Bz and PPEF. PPEF could be promptly superposed into the zonal equatorial electric field within minutes, producing similar frequent responses in EEJ. The large changes with low frequency are related to the disturbance wind dynamo electric field. Plain Language Summary: The interplanetary magnetic field (IMF) is the key to understand the interaction between solar wind and the Earth's magnetic field, hence space weather. In the observed IMF Bz, the characteristic of the periodic oscillation is common, ranging from several minutes and hours. When IMF Bz has an alfvenic wave nature, a relative perturbation of 5.51% ∼ 23.17% is observed in the equatorial electrojet (EEJ). The perturbations depend on the magnitude of the temporal oscillations of IMF Bz. EEJ has a prominent feature of short‐periodic oscillations with high frequency and a period of tens of minutes, which is dominated by the prompt penetration electric field. Key Points: An average relative perturbation of 17.5%, 5.51%, and 23.17% is generated in equatorial electrojet (EEJ) on August 24 in 2021, 2022, and 2023The short periodic changes with a period of tens of minutes are superposed into the perturbations of EEJThe prompt penetration electric field dominates the short periodic oscillations [ABSTRACT FROM AUTHOR]