The Chaotic or Non-chaotic Behavior of Global Geomagnetic Processes

Numerous linear studies of the geomagnetic indices have shown that the magnetospheric system is neither periodic nor quasiperiodic, and that only part of the AE variation can be explained as a direct linear response to the solar wind. This suggests the possibility that the magnetosphere is a non-linear system, and recent studies have been directed to determining whether the magnetospheric system behaves like a lowdimensional non-linear system. If the Earth’s magnetosphere can be shown to be low-dimensional, then not only can one make much better short term predictions of magnetospheric activity via non-linear techniques but also one may anticipate both improved magnetospheric models and a better understanding of the energy coupling between the solar wind and the magnetosphere. Conversely, a definite demonstration of the absence of low-dimensional behavior will help to guide future modelling efforts. Here, we present the basic tools of non-linear analysis, some of the problems to which they are heir, and some cures for those problems, followed by a review of the current evidence that the magnetosphere is a non-linear system.