Multifractality and punctuated equilibrium in the Earth's magnetic field polarity reversals.

The Earth's magnetic field has reversed its polarity hundreds of times in t he Earth's history. This phenomenon is generally viewed as due to a Poisson nonstationary process. Here, the geomagnetic chron time length sequence, f or the past 166 Ma, is analyzed using a multifractal approach, based on "si ngularity analysis". The existence of a multifractal structure is the signa ture of the occurrence of "punctuated equilibrium", which can be read as an indication of a critical configuration of the geodynamo. The results obtai ned are compared with those from a prototypical model of a dynamical system , introduced by Seki & Ito [1993], and are discussed in the context of flui d motions within the Earth's outer liquid core.