Reference Work Entry

Encyclopedia of Geomagnetism and Paleomagnetism

pp 161-163

Dynamo Waves

  • Graeme R. Sarson

Dynamo waves are oscillating solutions of the induction equation of magnetohydrodynamics (q.v.), which typically involve magnetic field fluctuations on global scales (possibly including global reversals), and fluctuate with periods related to the timescale of magnetic diffusion (i.e., ca. 103–104 years, for the Earth). They arise as oscillatory solutions of the kinematic dynamo problem (q.v.): the linear problem for the generation of magnetic field subject to the inductive action of a specified flow. The concept of dynamo waves can be extended beyond the linear regime, however, as the oscillatory behavior is often retained in nonlinear solutions; and in scenarios involving fluctuating velocities, such waves are invoked by several proposed mechanisms for geomagnetic reversals (see Reversals, theory).

In this usage, dynamo waves should be distinguished from other forms of magnetohydrodynamic waves (q.v.), including Alfvén waves (q.v.), and magnetic torsional oscillations (q.v.). The behav ...

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