Electron energy and electric field estimates in sprites derived from ionized and neutral <b><i>N</i></b>₂ emissions

Abstract

During the EXL98 aircraft mission, sprites and blue jets were observed by narrow band cameras that measure the N 2 + 1NG (0,1) band at 4278Å and the N 2 2PG (0,0) band at 3370Å. We discuss the observations (∼1km resolution), instrumental and atmospheric corrections, and altitude profiles of ionized (1NG) and neutral (2PG) emission observed during a specific sprite. The ratio of ionized‐to‐neutral emission indicates a relative enhancement of ion emission below 55km. Characteristic electron energies ( E Ch ) and electric fields ( E ) are derived from these emission ratios using excitation rates computed from a model that solves the Boltzmann equation as a function of electric field. Up to 55km E follows the breakdown field ( E k ) and E Ch is ∼2.2eV. Above 55km E drops below E k and E Ch drops to ∼1.75eV near 60km.