Determination of equilibrium electron temperature and times using an electron swarm model with BOLSIG+ calculated collision frequencies and rate coefficients

• Published in: Journal of geophysical research. Atmospheres 2015-08, Vol.120 (15), p.7300-7315
• Main Authors: Pusateri, Elise N., Morris, Heidi E., Nelson, Eric M., Ji, Wei
• Format: Article
• Language: English
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ATOMIC AND MOLECULAR PHYSICS; Coefficients; Collision dynamics; Conduction; Conduction electrons; Cross sections; Differential equations; Electric field; Electric fields; electron collision frequency; electron cross sections; Electron drift velocity; Electron energy; electron energy distribution; Electron swarms; electron temperature; Energy transfer; Equilibrium; Evolution; Geophysics; Ionization; Ionization coefficients; Mathematical models; Momentum; Momentum transfer; Ordinary differential equations; Parameters; Photoelectrons; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; swarm model; Temperature; Temperature effects; Velocity
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1002/2015JD023100

Electromagnetic pulse (EMP) events produce low‐energy conduction electrons from Compton electron or photoelectron ionizations with air. It is important to understand how conduction electrons interact with air in order to accurately predict EMP evolution and propagation. An electron swarm model can be used to monitor the time evolution of conduction electrons in an environment characterized by electric field and pressure. Here a swarm model is developed that is based on the coupled ordinary differential equations (ODEs) described by Higgins et al. (1973), hereinafter HLO. The ODEs characterize the swarm electric field, electron temperature, electron number density, and drift velocity. Important swarm parameters, the momentum transfer collision frequency, energy transfer collision frequency, and ionization rate, are calculated and compared to the previously reported fitted functions given in HLO. These swarm parameters are found using BOLSIG+, a two term Boltzmann solver developed by Hagelaar and Pitchford (2005), which utilizes updated cross sections from the LXcat website created by Pancheshnyi et al. (2012). We validate the swarm model by comparing to experimental effective ionization coefficient data in Dutton (1975) and drift velocity data in Ruiz‐Vargas et al. (2010). In addition, we report on electron equilibrium temperatures and times for a uniform electric field of 1 StatV/cm for atmospheric heights from 0 to 40 km. It is shown that the equilibrium temperature and time are sensitive to the modifications in the collision frequencies and ionization rate based on the updated electron interaction cross sections. Key Points An electron swarm model is improved using BOLSIG+ and updated cross sections Improved model is validated by comparing experimental data Temperature evolution is shown to be sensitive to scattering cross sections