  Instabilities in relativistic magnetized jets are thought to be deeply
connected to their energy dissipation properties and to the consequent
acceleration of the non-thermal emitting relativistic particles. Instabilities
lead to the development of small scale dissipative structures, in which
magnetic energy is converted in other forms. In this paper we present
three-dimensional numerical simulations of the instability evolution in highly
magnetized plasma columns, considering different kinds of equilibria. In fact,
the hoop stresses related to the azimuthal component of magnetic field can be
balanced either by the magnetic pressure gradient (force-free equilibria, FF)
or by the thermal pressure gradient (pressure-balanced equilibria, PB) or by a
combination of the two. FF equilibria are prone to current-driven instabilities
(CDI), while PB equilibria are prone to pressure-driven instabilities (PDI). We
perform a global linear stability analysis, from which we derive the different
instability properties in the two regimes, showing that PDI have larger growth
rates and are also unstable for high wavenumbers. The numerical simulations of
the non-linear instability evolution show similar phases of evolution in which
the formation of strong current sheets is followed by a turbulent quasi
steady-state. PDI are however characterized by a faster evolution, by the
formation of smaller scale dissipative structures and larger magnetic energy
dissipation.
