KINETIC HELICITY, MAGNETIC HELICITY AND FAST DYNAMO ACTION

The influence of the flow helicity on kinematic fast dynamo action is considered. Three different flows are studied, possessing identical ch aotic properties but very different distributions of helicity (maximal helicity, zero net helicity and zero helicity density). All three flo ws provide strong evidence of fast dynamo action, indicating that heli city is not a crucial feature of fast dynamo flows. Comparisons are ma de between the magnetic fields generated by the three flows and it is established how certain key quantities scale with the magnetic Reynold s number. In particular, it is shown that the relative magnetic helici ty tends to zero as the magnetic Reynolds number tends to infinity.