The solar-wind driven magnetosphere–ionosphere system is a classic example of a complex dynamical system (CDS). The defining properties of a CDS are (1) sensitivity to initial conditions; (2) multiple space-time scales; (3) bifurcation sequences with hysteresis in transitions between attractors; and (4) noncompositionality. Noncompositionality means that the behavior of the system as a whole is different from the dynamics of its subcomponents taken with passive or no couplings. In particular the dynamics of the geomagnetic tail plasma depends on its coupling to the dissipative ionospheric plasma and on the nature of the solar-wind driving electric field over a suitably long (many hours) previous time interval. These complex dynamical system features are shown here in detail using the known WINDMI model for the solar-wind driven magnetosphere–ionosphere (MI) system. Numerous features in the bifurcation sequence are identified with known substorm and storm characteristics.
Abstract.Using the methods of multi-and partial-linearcorrelation, we demonstrate that both the solar wind density and the solar wind electric field make significant and independent contributions to the strength of the ring current, as measured by the Dst* index, during mild storms. The solar wind data were obtained from WIND, and the Dst data from OmniWeb. After appropriate cleaning of the data, 55 events from the Wind-era with Dst* excursions below -50 were obtained.Correlations with Dst* were performed with independent, variable time lags for the density and for the electric field, and the optimal time lags are found to be approximately 5 hours for density and less than one hour for the electric field (in addition to the time shift to Earth).
Abstract. This paper explores the dynamical range of the WINDMI model (Horton and Doxas, 1998]. Such low-dimensional models provide us with the tools to understand the relationships of simple physical quantities within the magnetosphere (such as energy deposition, macroscopic currents, cross-tail voltage, etc.) without the necessity of coping with the more complete but unwieldy models (MHD or particle codes, for example). The model is highly versatile: certain regions of the parameter space support stable fixed points, while others contain periodic states that exhibit period doubling, and sometimes chaos. States in each of these regimes (stable, periodic, chaotic) are investigated for their ability to accurately describe the observed properties of the magnetosphere-ionosphere system. A brief discussion of applications of this model to current space physics problems is included.
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