Electron energy distribution from intense electron beams in the upper mesosphere and lower thermosphere

A model was developed to calculate the electron energy spectrum created by an electron beam in the upper atmosphere. A significant feature of the model is the inclusion of the effects of electron‐electron collisions which are important at high beam intensity when the ratio of the electron to ambient gas density is high. Comparing the calculated results for a 2.6‐kV, 20‐A beam at 110‐km altitude from models with and without the electron‐electron collision term, the electron‐electron collisions have the effect of smoothing out the electron spectrum in the low‐energy region (<10 eV). In particular, the “bite‐out” features of the spectrum induced by the vibrational excitation of N 2 and O 2 are filled in, resulting in an increase in the calculated production rate of these species compared with model calculations that neglect this effect.