  Using high resolution adaptive mesh refinement simulations in 3D, we
investigate the formation of relativistic jets from rotating magnetospheres.
Here, we focus on the development of non-axisymmetric modes due to internal and
external perturbations to the jet. These originate either from injection of
perturbations with the flow or from a clumpy external medium. In the helical
field geometry of the accelerating jet, the m=1 to m=5 modes are analyzed and
found to saturate at a height of \sim 20 inner disk radii. We also discuss a
means to control artificial amplification of m = 4 noise in the cartesian
simulation geometry. Strong perturbations due to an in-homogeneous ambient
medium lead to flow configurations with increased magnetic pitch and thus
indicate a self-stabilization of the jet formation mechanism.
