Non‐Maxwellian Characteristics of the Energy Distribution of Thermal Electrons in the Upper Atmosphere

Abstract

AbstractThe Result of Measurements of the energy distribution of thermal electrons in a midlatitude ionosphere is presented. A comparison is made in particular between the characteristics at sunrise and sunset periods because of the effect of vibrationally excited nitrogen molecules.At sunrise the distribution has a little‐irregularity but the middle and higher energy parts (0.2‐0.5 eV) deviate from the Maxwellian distribution only slightly at all heights. The electron temperature varies from 900 K to 1300 K between 130 km and 300 km. These values are higher than the kinetic temperature of neutral particles but comparable with the theoretical values of the vibration temperature of N2.At sunset small bumps due to non‐thermal electrons are seen on the high energy tail between 108 and 160 km, their density being from 5 × 10−3 to 1 × 10−2 of that one of the thermal electrons. Above 170 km (F‐layer) the deviation of the distribution from the Maxwellian one becomes smaller. The electron temperature varies from 500 K to 900 K between 100 km and 220 km. These values are higher than the kinetic temperature but lower than the theoretical values of the vibration temperature of N2. A mechanism of the appearance of non‐thermal electrons is considered to be due to super‐elastic collisions with vibrationally excited N2.