Evidences of a distorted electron energy distribution in ionospheric plasma

The energy distribution of thermal electrons in the ionospheric plasma was measured by means of a glass-sealed Langmuir probe. Second derivatives of the v-i curves were obtained electrically by using the second harmonic method. The height of the measurement was from 103 to 360 km.Above 130 km the energy distribution of thermal electrons were Maxwellian enough to evaluate electron temperature. Below 130 km the electrons appeared to consist of two groups of electrons of different temperatures. Because of the bi-Maxwellian energy distribution, the apparent electron temperature obtained from the above method differed from that of an electron temperature probe.