Simulated AA-fluctuations computed directly from the perturbed wavefront phase and observed as intensity fluctuations in the pupil plane image. a) and b) are respectively x and yAA components at the entrance pupil, while c) is the y component observed in the pupil plane image as intensity fluctuations. The perturbed wavefront was simulated in the near-field approximation case considering r₀ = 4 cm, ℒ₀ = 10 m, and h = 1000 m. The diaphragm width was taken as equal to a few arcseconds.