Similarities between the dynamics of geomagnetic signal and of heartbeat intervals

¹  Departamento de Física, Universidade Estadual de Maringá - Avenida Colombo 5790 87020-900, Maringá-Paraná, Brazil
²  Observatório Nacional - Rua General José Cristino 77, 20921-400 Rio de Janeiro, RJ, Brazil
³  Instituto de Física, Universidade do Estado do Rio de Janeiro - Rua São Francisco Xavier 524 20550-900, Rio de Janeiro, RJ, Brazil

Received: 20 February 2007
Accepted: 3 October 2007

Abstract

We analyze the dynamics of a widely used measure of geomagnetic activity —the Dst index— and compare our findings with those found in healthy human heartbeat dynamics. We show that the Dst index belongs to a special class of complex signals, exhibiting long-range temporal correlations, multifractality and scale-invariant distribution. Specifically, we find that i) Dst series and magnitude series of Dst increments are long-range correlated while the sign series of Dst increments is anti-correlated; ii) the scaling exponents that govern these temporal correlations increase with geomagnetic activity; iii) Dst series exhibit multifractal behavior; iv) the multifractal spectra that characterize Dst series are practically independent of the geomagnetic activity; and v) the distribution of Dst increments exhibits scale invariance at a wide range of time scales. These results are in surprising agreement with those found in the study of heartbeat intervals. Our findings are consistent with the concept of universality in complex systems and may contribute to a better understanding of the mechanisms that govern geomagnetic activity.