README.md

2026AH

Codex/ChatGPT (July 2026)

Summary

This paper derives a nonlinear fourteen-moment electron closure for rarefied, nonmagnetized, partially ionized plasmas where strong fields and finite electron drift invalidate linearized transport theory. A Hermitian velocity-distribution expansion evolves density, momentum, the anisotropic pressure tensor, contracted heat flux, and scalar kurtosis. Collision moments are integrated analytically at finite Mach number for elastic and inelastic electron-neutral interactions, electron-impact ionization, and electron-electron and electron-ion Coulomb collisions. The resulting terms couple moments of different tensorial rank, breaking the linear-regime Curie symmetry; examples include pressure-anisotropy effects on momentum and inelastic rates and kurtosis effects on heat-flux relaxation. In homogeneous argon calculations over $10$--$1000$ Td, the nonlinear model agrees substantially better with Monte Carlo collision results than linear 13- or 14-moment models, particularly above $100$ Td and before runaway. It also captures high-order moments and high-energy-distribution depletion missed by linear closures.

Contributions

1. Formulated a nonlinear 14-moment model for density, velocity, anisotropic pressure, heat flux, and scalar kurtosis.
2. Integrated finite-drift nonlinear collision moments analytically for elastic, inelastic, ionization, and Coulomb processes.
3. Identified cross-tensorial collisional couplings absent from linear closures.
4. Quantified large anisotropy- and kurtosis-dependent corrections to collision rates.
5. Demonstrated substantially better agreement with Monte Carlo kinetics than linear closures through $1000$ Td.