In the present paper we investigate the influence of tensorial viscosity on
the linear MHD spectrum for isolated twisted magnetic flux tubes surrounded by
vacuum.
The magnetic flux tubes are modelled as 1D cylindrical plasma columns.
Viscosity is described by its classical tensorial form with compressive and
shear viscosity. The equilibrium parameters of the flux tube are choosen
to model coronal loops.\newline
Numerical simulations show that in ideal MHD a poloidal magnetic field can
destabilize the magnetic structure. They also show that viscosity can strongly
destabilize the magnetic structure. This destabilization depends on the poloidal component of the magnetic field.