The equatorial electrojet (EEJ) has an abnormally large amplitude of variations in the horizontal components due to the strength of the lunar tides.
Because of this, the pressure and temperature of the lower atmosphere vary, and the effects propagate upward in a tidal wave form to the E region and modulate the electrodynamics.
A typical diurnal equatorial observatory data show a peak of strength ~80 nT at 12:00 LT, with respect to the night-time level.
Egedal (1947) showed that the enhancement of quiet day solar daily variations in ΔH (Sq(H)) lay within the 50 latitude centered on the dip equator.
The mechanism that produced the variation in the magnetic field was proposed as a band of current about 300 km in width flowing over the dip equator.
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.
EEJ magnetic signals measured by Ettaiyapuram Magnetic Observatory, India ( ETT - Operated by National Geophysical Research Institute, NGRI, Hyderabad). These data are averages of the daily difference between magnetic data (H) at Ettaiyapuram and Hyderabad collected over several years. The horizontal intensity of magnetic field peaks at ~12 LT. The buildup flank in the morning hours is steeper than that of the decay phase. .
A movie of the variation of the geomagnetic field at the surface of the Earth due to the ionsopheric current systems. The equatorial intensification of the magnetic field is due to the Equatorial Electrojet (EEJ). UT = universal time. The unit is nT (nanotesla). The movie was generated using a geomagnetic field model (CM4).
