Characterization of experimental dynamos

SUMMARY Laboratory models of geophysical magnetic ¢eld production require new experimental characterization methods. Self-generating liquid metal magnetic dynamos are explored using two new experiments. Kinematic dynamo studies lead us to characterize the magnetic ¢eld dynamics in terms of eigenvalues and eigenfrequencies of the induction equation. Observing the decay of magnetic ¢eld pulses indicates the real part of the leading eigenvalue of the induction equation, while a chirp magnetic ¢eld diagnoses the imaginary part of the eigenvalue. Finally, a single-frequency applied magnetic ¢eld characterizes the structure of the velocity ¢eld. These measurements provide a new means to characterize and measure the approach to self-generation. We present data from numerical simulations and laboratory experiments using these techniques.