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Dynamo action in christopherson hexagonal flow

Abstract Kinematic dynamo action is investigated for the Chiistopherson flow consisting of a horizontally periodic layer of identical hexagonal cells. In each cell a conducting fluid ascends at its centre and descends at its periphery. Boundary conditions are chosen so that the layer has a perfectly conducting base and is overlaid by a current-free atmosphere. By numerically solving the eigenvalue problem for the induction equation, it is found that a dynamo operates when the magnetic Reynolds number R m exceeds 515. According to recent theoretical results, this dynamo is expected to be slow, though our results show the growth rate is still increasing at R m= 1000. The magnetic structure is concentrated around stagnation points and their associated heteroclinic orbits.