**Publication date:** Apr 2014

**Abstract:**

The problem of the transition from gas to plasma in gravitating

axisymmetric structures is addressed under the assumption of having

initial and final states realized by kinetic Maxwellian-like equilibria.

In astrophysics, the theory applies to accretion-disc scenarios around

compact objects. A formulation based on non-relativistic kinetic theory

for collisionless systems is adopted. Equilibrium solutions for the

kinetic distribution functions describing the initial neutral matter and

the resulting plasma state are constructed in terms of single-particle

invariants and expressed by generalized Maxwellian distributions. The

final plasma configuration is related to the initial gas distribution by

the introduction of appropriate functional constraints. Qualitative

aspects of the solution are investigated and physical properties of the

system are pointed out. In particular, the admitted functional

dependences of the fluid fields carried by the corresponding equilibrium

distributions are determined. Then, the plasma is proved to violate the

condition of quasi-neutrality, implying a net charge separation between

ions and electrons. This result is shown to be independent of the

precise realization of the plasma distribution function, while a

physical mechanism able to support a non-neutral equilibrium state is

proposed.

**Authors:**

Cremaschini, Claudio; Stuchlík, Zdeněk;