Comparison between the analytical dispersion relation (in plain lines) and the numerically measured growth rates (markers). Black diamonds are the numerical growth rates of the most unstable modes with n = 0, found in the first simulation seeded with low amplitude random white noise on the velocity field. They match the theoretical dispersion relation to within ζ ≲ 1%. The blue star depicts the MTI eigenmode with m = 92 and n = 1, which could be successfully isolated in the same simulation. The purple circle stands for the numerical growth rate of the MTI eigenmode with m = 101 and n = 0. It agrees with the theoretical dispersion relation to within ζ ≈ 2.0% only. The green triangle represents the numerical growth rate of the exact same mode, but in a simulation seeded with a single mode. The error is very small, ζ ≈ 0.027%.