Horizontal distribution of helium in the Earth's upper atmosphere

The helium distribution in June 1969 was studied by using data from the mass spectrometer on Ogo 6 (perigee, 400 km; apogee, 1100 km). After normalizing for altitude effects by use of the Jacchia model atmosphere, the densities show an order of magnitude difference between the southern (winter) hemisphere and the northern (summer) hemisphere, with the maximum density occurring near −55° latitude. The exact location of the maximum varies between −40° and −70° geographic latitude and is apparently correlated with the geomagnetic dipole latitude of −53°. This correlation is consistent with the idea that the helium distribution is quite sensitive to thermospheric winds.