THE ROLE OF ELECTRIC FIELDS AND MAGNETOSPHERIC ELECTRON PRECIPITATIONS FOR THE FORMATION OF THE EQUATORIAL TOTAL MASS DENSITY MINIMUM

The global theoretical Upper Atmosphere Model (UAM) shows a minimum of the thermospheric total mass density near the geomagnetic equator similar to that obtained by the accelerometer on board the CHAMP satellite. The empirical thermospheric model NRLMSISE-00 does not show this minimum. We have investigated the role of electric fields and magnetospheric electron precipitations for the formation of this daytime minimum by successive switching off the low and high latitude electric fields and the magnetospheric electron precipitations within the UAM calculations. We conclude that the high latitude magnetospheric heating is the likely reason of the daytime thermospheric density minimum near the equator.