Equatorial electrojet

A snapshot of the variation of the Earth's magnetic field from its intrinsic field at 400 km altitude, due to the ionospheric current systems. The equatorial intensification of the magnetic field is due to the equatorial electrojet (EEJ). The EEJ peaks over the Indian Ocean at the point in time depicted. The map was generated using a geomagnetic field model.

The equatorial electrojet (EEJ) is a narrow ribbon of current flowing eastward in the day time equatorial region of the Earth's ionosphere. The abnormally large amplitude of variations in the horizontal components measured at equatorial geomagnetic observatories, as a result of EEJ, was noticed as early as 1920 from Huancayo geomagnetic observatory. Observations by radar, rockets, satellites, and geomagnetic observatories are used to study EEJ.