On the stability of anisotropic astrophysical jets

The presence of magnetic fields in low density extragalactic radio jets may cause a decoupling of the particle velocities parallel and perpendicular to the magnetic field direction. Consequently the anisotropic plasma pressure must be taken into account in the theoretical models on the structure and evolution of jets. In this paper the authors discuss the stability of a cylindrical beam in the framework of the double adiabatic theory of Chew, Goldberger & Low (1956) for the description of a magnetized plasma with anisotropic pressure. The authors find that, in contrast with previous studies based on isotropic hydrodynamics (or MHD), jets can be highly unstable for any velocity, and that unconfined (free) jets may also undergo the instability process.