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Determine whether entry and exit arise from stochastic fluctuations in the Babcock-Leighton poloidal source (scatter of active-region tilt angles, rare anomalous active regions), from nonlinear deterministic dynamo dynamics, or from changes in meridional flow, and whether the waiting-time distribution is exponential. Answer: a model reproducing the frequency and duration distribution of grand minima and the hemispheric asymmetry of the Maunder Minimum.","problem_ref":"9f03e1f2ddf9f19687c7edd1effce2a7ca04aeddba0cfeccc945111b9eb95c85","references":"","settled_by":"Dynamo models calibrated on observed tilt-angle statistics whose simulated grand-minimum statistics agree with the isotope record.","status_note":"","title":"What causes grand minima such as the Maunder 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