Electron temperature was measured by means of planar probes on Japan's ninth scientific satellite OHZORA. The measurement, which was carried out simultaneously both along the vertical to the geomagnetic line of force, showed anisotropy of electron temperature. The temperature of the electrons along the geomagnetic field, T∥, is very often higher than the temperature of electrons collected by the electrode whose normal is perpendicular to the geomagnetic field, T⊥. Anisotropy increases as we move to higher geomagnetic latitudes. Anisotropy occurs more often in the early morning than at any other time of day. There is also a tendency for anisotropy to occur more often at lower altitudes.

It is suggested that the existence of anisotropy of electron temperature can explain some puzzling phenomena that have previously not been explained. ¿ American Geophysical Union 1987