Summary: Investigating dynamical complexity in the magnetosphere using
various entropy measures
Ioannis A. Daglis,1
and Konstantinos Eftaxias2
Received 30 December 2008; revised 25 February 2009; accepted 11 March 2009; published 10 June 2009.
 The complex system of the Earth's magnetosphere corresponds to an open spatially
extended nonequilibrium (input-output) dynamical system. The nonextensive Tsallis
entropy has been recently introduced as an appropriate information measure to investigate
dynamical complexity in the magnetosphere. The method has been employed for
analyzing Dst time series and gave promising results, detecting the complexity
dissimilarity among different physiological and pathological magnetospheric states
(i.e., prestorm activity and intense magnetic storms, respectively). This paper explores the
applicability and effectiveness of a variety of computable entropy measures (e.g., block
entropy, Kolmogorov entropy, T complexity, and approximate entropy) to the investigation
of dynamical complexity in the magnetosphere. We show that as the magnetic storm
approaches there is clear evidence of significant lower complexity in the magnetosphere.