Helical magnetorotational instability in a TaylorCouette flow

We analyze numerically the magnetorotational instability (MRI) of a hydrodynamically stable Taylor-Couette flow with a helical external magnetic field in the inductionless approximation defined by a zero magnetic Prandtl number. The Chebyshev collocation method is used to calculate the eigenvalue spectrum for small amplitude perturbations. Besides the convective instability threshold also an absolute one is found implying that this type of MRI might be experimentally observable in a system of sufficiently large but finite axial extension.