MULTIPLE SCALE DYNAMO

A scaling law approach is used to simulate the dynamo process of the E arth's core, The model is made of embedded turbulent domains of increa sing dimensions, until the largest whose size is comparable with the s ite of the core, pervaded by large-scale magnetic fields, Left-handed or right-handed cyclones appear at the lowest scale, the scale of the elementary domains of the hierarchical model, and disappear, These ele mentary domains then behave like electromotor generators with opposite polarities depending on whether they contain a left-handed or a right -handed cyclone, To transfer the behavior of the elementary domains to larger ones, a dynamic renormalization approach is used. A simple rul e is adopted to determine whether a domain of scale l is a generator-a nd what its polarity is-in function of the state of the (l - 1) domain s it is made of, This mechanism is used as the main ingredient of a ki nematic dynamo model, which displays polarity intervals, excursions, a nd reversals of the geomagnetic field.