The transient and steady-state expansion of a weakly-collisional plasma beam in a paraxial magnetic nozzle is studied with a kinetic Boltzmann–Poisson model. Only intraspecies collisions involving electrons are considered and these are modeled with a Bhatnagar–Gross–Krook operator. Simulations show that occasional collisions progressively populate the phase-space region of isolated trapped electrons until a steady state is reached, which is independent of transient history. The steady state is characterized by a partial occupancy of that region increasing with the collisionality rate but far away from the full occupancy postulated by an alternative steady-state kinetic model. The changes on the amount of trapped electrons with the collisionality rate explain, in turn, the changes on the spatial profiles of main plasma magnitudes. Conclusions on the momentum and energy balances of ions and electrons agree, in terms of general trends, with those of the steady-state kinetic model. In the downstream region of the expansion, ions and electrons lose all their perpendicular energy but they still keep part of their parallel thermal energy. Electron heat fluxes of parallel energy are not negligible and are approximately proportional to enthalpy fluxes.

使用动力学 Boltzmann-Poisson 模型研究了近轴磁喷嘴中弱碰撞等离子体束的瞬态和稳态膨胀。只考虑涉及电子的种内碰撞，这些碰撞使用 Bhatnagar-Gross-Krook 算子建模。模拟表明，偶尔的碰撞会逐渐填充孤立的俘获电子的相空间区域，直到达到稳定状态，这与瞬态历史无关。稳态的特点是该区域的部分占有率随着碰撞率的增加而增加，但与另一种稳态动力学模型假设的完全占有率相差甚远。捕获电子数量随碰撞率的变化反过来解释了主要等离子体大小空间分布的变化。关于离子和电子的动量和能量平衡的结论就总体趋势而言与稳态动力学模型的结论一致。在膨胀的下游区域，离子和电子失去了所有的垂直能量，但它们仍然保留了部分平行热能。平行能量的电子热通量不可忽略并且与焓通量近似成正比。