Some Features of Night Time Electron Density and Temperature in the 2, 500km Region of the Exosphere

Abstract

The Alouette 2 electrostatic probe measurements of electron density and electron temperature during 1966-1967 show several interesting features in the nighttime 2, 000-3, 000km altitude region. There are seasonal differences in the latitudinal variation of the electron parameters, with N_e forming nocturnal peaks at ±40°geomagnetic latitude during solstices; the summer peak value exceeds the winter peak by almost 50%. The relationship between N_e and T_e for these altitudes appears to be rather dependent on latitude, and also exhibits seasonal differences. The T_e peak at mid-latitudes forms at a location about 5°lower in geomagnetic latitude than the N_e plasmatrough minimum, and coincides with the lower latitude cliff of the trough.
The ionic mass in the 2, 500km region is estimated from the observed values of N_e and T_e; the values obtained identify with the light ions H⁺ and He⁺ between 0 and 40°geomagnetic latitude and a heavy ion species at higher latitudes. The effect of magnetic activity is to decrease N_e and to increase T_e at latitudes within ±50°. The plasmatrough in N_e and the corresponding T_e peak show a clear equatorward movement during geomagnetic disturbance.