Abstract
AbstractThe equatorial electrojet (EEJ) is a band of zonal electric current flowing along the magnetic equator in the dayside E‐region ionosphere. The direction of the EEJ is often eastward but sometimes westward. The mechanism for generating westward EEJ is not fully understood. This study examines the relationship between the eastward/westward EEJ and equatorial neutral winds using simultaneous observations of the EEJ from the European Space Agency's Swarm satellite mission and thermospheric winds from the Michelson Interferometer for Global High‐resolution Thermospheric Imaging on NASA's Ionospheric Connection Explorer mission during December 2019–January 2021. Significant differences are found in the average zonal wind profiles between times of eastward and westward EEJ. The EEJ intensity correlates negatively (R = −0.54) and positively (R = 0.58) with the eastward wind velocities at ∼110 and ∼140 km, respectively. The results suggest that the modulation of the zonal electric field by the equatorial zonal wind plays a role in producing the westward EEJ.
Highlights
Collisional interactions between neutral and plasma particles at the E-region heights lead to the production of electric fields and currents, which can be expressed as follows: where J is the current density, ˆ is the ionospheric conductivity tensor, E is the electric field, U is the neutral wind, and B is the ambient magnetic field
This study examines the relationship between the eastward/westward EEJ and equatorial neutral winds using simultaneous observations of the EEJ from the European Space Agency's Swarm satellite mission and thermospheric winds from the Michelson Interferometer for Global High-resolution Thermospheric Imaging on National Aeronautics and Space Administration (NASA)'s Ionospheric Connection Explorer mission during December 2019–January 2021
Simultaneous observations of the Swarm equatorial electrojet (EEJ) intensity and Ionospheric Connection Explorer (ICON)/Michelson Interferometer for Global High-Resolution Thermospheric Imaging (MIGHTI) thermospheric wind velocities are analyzed for the period from December 2019 to January 2021 under quiet geomagnetic activity conditions (Hp30
Summary
Collisional interactions between neutral and plasma particles at the E-region heights (ca. 90–150 km) lead to the production of electric fields and currents, which can be expressed as follows: where J is the current density, ˆ is the ionospheric conductivity tensor, E is the electric field, U is the neutral wind, and B is the ambient magnetic field. 90–150 km) lead to the production of electric fields and currents, which can be expressed as follows: where J is the current density, ˆ is the ionospheric conductivity tensor, E is the electric field, U is the neutral wind, and B is the ambient magnetic field. Large-scale motion of the atmosphere across the geomagnetic field drives electric currents on the dayside ionosphere, where the conductivity is enhanced due to photoionization mainly by solar extreme ultraviolet radiation. The electric field in the low-latitude ionosphere is usually eastward on the dayside. The zonal electric field sets up a vertical polarization electric field near the magnetic equator, which drives the zonal current in the same direction as the current driven by the zonal electric field. There is a band of enhanced current flowing along the magnetic equator, which is known as the equatorial electrojet (EEJ) (e.g., Forbes, 1981; Yamazaki & Maute, 2017)
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