Regimes of expansion of a collisional plasma into a vacuum
Résumé
The effect of elastic Coulomb collisions on the one-dimensional expansion of a plasma slab is studied in the classical limit, using an electrostatic particle-in-cell code. Two regimes of interest are identified. For a collision rate of few hundreds of the inverse of the expansion characteristic time $ \tau_e$ the electron distribution function remains isotropic and Maxwellian with a homogeneous temperature, during all the expansion. In this case, the expansion can be approached by a three-dimensional version of the hybrid model developed by Mora [P. Mora, Phys. Rev. E 72, 056401 2005]. When the collision rate becomes somewhat greater than $10^4 \tau_e^{-1}$ the plasma is divided in two parts: an inner part which expands adiabatically as an ideal gas and an outer part which undergoes an isothermal expansion.
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