Effect of kinetic anisotropies on the beta parameter in collisionless magnetized non-ideal plasma fluids

It is demonstrated that collisionless magnetized plasma fluids at equilibrium characterized by the occurrence of phase-space kinetic anisotropies exhibit a lower beta parameter with respect to corresponding isotropic configurations. The theoretical framework is provided by statistical kinetic formulation of plasma physics based on the Vlasov equation in both relativistic and non-relativistic regimes. The proof relies on the analytical construction of non-isotropic Gaussian-like kinetic distribution functions (KDFs) that are consistent with microscopic single-particle exact or adiabatic conservation laws. These KDFs generate corresponding non-ideal magnetized plasma fluids characterized by non-isotropic pressure tensors. A depletion of the magnitude of directional plasma pressure components compared to the thermal isotropic scalar pressure is shown to occur, that is induced by phase-space anisotropies. It is pointed out that this physical principle enhancing low-beta states can represent a mechanism contributing the self-confinement of magnetized plasmas at equilibrium. Relevant applications concern high-energy astrophysical scenarios characterized by intense background magnetic fields, with particular reference to asymptotically steady states of collisionless plasmas forming non-ideal fluids in toroidal structures or relativistic jets.