Abstract
The geodynamo has widely been thought to be an intuitive and selfsustained model of the Earth’s magnetic field. In this paper, we elucidate how a periodic signal could be embedded in the geomagnetic filed via the mechanism of stochastic resonance in a forced Rikitake dynamo. Based on the stochastic resonance observed in the periodically forced Rikitake dynamo, we thus suggest a common triggering for geomagnetic reversal and glacial events. Both kinds of catastrophes may result from the cyclic variation of the Earth’s orbital eccentricity.
Highlights
The Reynolds number of the Earth’s liquid core is believed to be sufficiently large (~108)that the flow of electrical currents in the liquid core is undoubtedly turbulent (e.g., Glatzmaier 2002)
At the end of this paper, we propose an interesting implication for the observed stochastic resonance (SR) phenomenon to explain the coincident temporal correlation between geomagnetic reversal and glacial events, for which both have a common quasi-period of about 100 kyr (e.g., Yokoyama and Yamazaki 2000)
No theoretical analysis can explain the coincident temporal correlation between the geomagnetic reversal and glacial events yet, for which both have a quasi-period of about 100 kyr, there exists a good deal of observational evidence for such a correlation
Summary
The Reynolds number of the Earth’s liquid core is believed to be sufficiently large (~108). While the actual Earth’s dynamo is absolutely a high-order physical system with very large degrees of freedom (Glatzmaier and Roberts 1995; Buffett 2000; Hoyng et al 2002), the Rikitake dynamo is only a low-order analog with few degrees of freedom that oversimplifying the electrical current flows in the liquid outer core. The term stochastic resonance describes the group of effects in a nonlinear system whereby the response of the system to the weak external, periodic signal is remarkably amplified by an increase in noise intensity This idea was independently introduced by Benzi et al (1981) and Nicolis (1982) in an attempt to explain the peculiar phenomenon of periodic recurrence in the Earth’s ice ages. It is natural that SR can be observed (e.g., Carroll and Pecora 1993; Arai et al 2004) in various deterministic chaotic systems without the presence of noise, the Rikitake dynamo for example
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