The magnetospheric response to the solar wind input, as represented by the time series measurements of the AE index, has been examined using phase space reconstruction techniques. The system was found to behave as a low-dimensional chaotic system with a fractal dimension of 3.6 and has a Kolmogorov entropy <0.2/min. These are indicative that the dynamics of the system can be adequately described by four independent variables and a corresponding intrinsic time scale is of the order of 5 min. The relevance of the results to magnetospheric modelling is discussed. ¿American Geophysical Union 1990