Kinetics of Molecular Nitrogen Triplet Bands at Low Air Pressure

High-altitude atmospheric discharges strongly affect the origination and movement of charged particles in the Earth’s atmosphere, in particular, impact communication lines. Their variability and the complexity of the related physical processes cause the interest to them among researchers all over the world. This work studies the kinetics processes of molecular nitrogen triplet bands in air at pressures of 0.03–1 torr. Simulation results and experimental measurements show the dependence of the ratios of the spectral density of radiation energy of four bands of the first positive system of nitrogen to two bands of the second positive system of nitrogen, i.e., an increase in the ratio with a decrease in the air pressure. This dependence is because of an increase in the rate of quenching B3Πg state of nitrogen molecules with an increase in the air density. These results explain a change in the color of red sprites with a decrease in the altitude above sea level starting from about 50 km.