Vibrational kinetics of air plasmas induced by sprites

Abstract

The vibrational kinetics of air plasmas produced by the presence of sprites in the mesosphere of the Earth is studied in detail. The present model solves the coupled electron Boltzmann equation and rate equations for electrons, neutrals (ground and excited), and ions. Special attention is paid to the vibrational kinetics of N2 (X1Σg+) and to that of the N2 triplet states (A3Σu+, B3Πg, C3Πu, W3Δu, and B′3Σu+). The results presented are for an altitude of 78 km over sea level where the model‐predicted vibrational distribution function (VDF) of N2 (B3Πg) is in agreement with available VDF derived from sprite spectra (640–820 nm) obtained using spectrographs coupled to high‐speed video cameras (300 frames per second (fps)). In addition, the model predictions indicate that the sprite plasma VDFs of N2 (B3Πg) and N2 (C3Πu) are almost in thermal equilibrium and exhibit a maximum at v = 0 followed by lower values for v = 1 and v = 2. Finally, it is also predicted that the N2 (B3Πg) and N2 (C3Πu) VDFs recorded with very high speed video cameras (up to 10000 fps) should not differ much from the N2 (B3Πg) and N2 (C3Πu) VDFs obtained with cameras working at lower speeds (30 and 300 fps).