Characterizing the Effect of Substorms on the Equatorial Electrojet

Johns Hopkins University, Baltimore MD

Investigators

Abstract

The equatorial electrojet (EEJ), an intensified electric current flowing eastward in the ionosphere during daytime hours. The work will investigate whether the EEJ weakens or strengthens during substorms. Successful completion of this project will not only resolve this controversy but will also significantly improve our overall understanding of the global current circuit. Understanding how the upper atmosphere at the auroral region couples with that at low latitudes is a crucial step for ensuring space weather awareness and mitigating the harmful effects of geomagnetic perturbations on technology, such as power grids, satellites, and communications. The investigators will address the questions related to the spatiotemporal characteristics of the EEJ and the interplanetary magnetic field (IMF) conditions during substorms. These are: (i.) How does the EEJ response to substorms vary with longitude, local time, season, and solar flux? (ii.) How do substorm duration, intensity, onset time, and IMF conditions affect the EEJ response? The methodology hinges on observational data and robust statistical analysis, leveraging NSF-supported projects, the SuperMAG network, and the Jicamarca Radio Observatory (JRO). Based on four well-known substorm lists, the research team intends to examine events during geomagnetic quiet periods and quasi-steady IMF conditions. These stringent criteria allow them to isolate the sole substorm effect and exclude unconnected factors like IMF variations known to impact the EEJ. The resulting magnetic field perturbations will be assessed using a well-established approach based on a pair of magnetometers, one positioned within ±3° of the dip equator and the other at an offset location (6°-10°). They will assess the related electric field variations via vertical ion drift measurements from the incoherent and coherent scatter radars at the JRO. The success of our proposal is sustained by the wealth of data and the expertise of the team. The investigation will provide new insights into the influence of EEJ response to substorms, thus providing new perspectives on how the electric fields penetrate from high to low latitudes, improving their understanding of the magnetosphere-ionosphere current system, and supplying essential parameters for future simulations. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.