Values of the angle θ for which the PIs grow super-exponentially. The rapid increase of the secondary modes occurs between θ₁ and θ₂, depicted with solid black lines. These lines correspond to the mean value of these angles for the runs from Table C.1. The red-shaded regions represent the 1-σ deviation. The black dashed line stands for the direction of the MRI velocity field, θ_V = 44.5°.