The (un)predictable magnetosphere: the role of the internal dynamics

Abstract

The magnetosphere–ionosphere dynamics comprises processes both directly related to solar wind variability and of purely internal origin. The latter represent a huge drawback for correctly forecasting the magnetosphere–ionosphere dynamics during geomagnetic storms and substorms. Here, we use wavelet analysis to further characterize the storm–substorm relationship through the use of the AL and SYM-H geomagnetic indices. We focus our analysis on one of the strongest geomagnetic storms of solar cycle 23 that occurred on 20 November 2003. Our findings suggest that, during disturbed periods, a significant amount of information comes from the interactions between geomagnetic storms and magnetospheric substorms. Thus, predicting the intensity and the duration of a geomagnetic storm requires information coming not only from the solar wind variability but also from the nonlinear variability of the magnetosphere–ionosphere system occurring on short time scales. Our results are also discussed in the framework of Space Weather, suggesting an extended use of non-traditional dynamical systems approaches (such as those based on extreme value statistics and tipping point analysis) to deal with emergent behaviours coming from different sources during geomagnetic storms and magnetospheric substorms.