Control of Inversions of the Earth’s Magnetic Field with Rikitake’s Model
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Abstract
Paleomagnetic data demonstrates that the Earth’s dipole magnetic field which shields the planet from solar wind, has undergone numerous irregular polarity reversals, with an average rate of approximately 5 per Myr. While many theories exist regarding the cause of these reversals, the most popular linking them to Milankovitch cycles, direct numerical investigation of the core's dynamo is constrained by the extreme parameter values of the Earth’s outer core. Consequently, simplified models are essential. One such model is the two-disk Rikitake’s dynamo, which is characterized by inherent chaotic inversions, unlike the earlier Bullard’s model. Statistical analyses show that the Rikitake’s model, much like real paleomagnetic data, exhibits a strong deviation from Poisson statistics. In this study, we modified the Rikitake’s system by introducing an external current corresponding to an external magnetic field. This modification incorporates the hypothesis that the geodynamo is influenced by the weak interstellar magnetic fields found in the Local Interstellar Cloud. Our results show that when the modified Rikitake’s model is driven by an external current whose sign changes are synchronized with real paleomagnetic data, the model successfully reproduces the timing of the geomagnetic reversals, supporting the hypothesis of external control of the geodynamo.
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