At these energies inelastic energy losses dominate over elastic ones and tends to 1, making modeling based on the simple considerations used in Section 2.1.2 essentially invalid. However, a detailed calculation of the distribution function from the Boltzmann equation which takes into account an appropriate set of inelastic collisions may result in a slightly more complex and structured distribution, for instance that calculated by Taranenko et al. The dominant inelastic processes for energized electrons in weakly ionized air are ionization and electronic excitation of neutrals, as already mentioned above, and electron attachment to neutrals. As a result of the third classical mechanics fact listed above, electrons cannot combine with electronegative species such as O or positive ions in a two-body collision. He thus predicted an electrical breakdown and ensuing optical emissions.
Streamers are ionization waves which can propagate as narrow channels through regions where .
This self-propagation is due to highly nonuniform electric fields which result from significant , or space charge. Streamer breakdown is not addressed in any detail in this work, but Section 2.3 provides references to recent overviews and to studies relating to sprites. Nevertheless, the issue of streamer initiation is addressed in the context of the observations presented in subsequent sections. The requirements for streamer initiation have mostly been discussed in the context of spark-gap experiments. For instance, Raizer et al.