Journal of Statistical Physics, Vol. 53, Nos. 3/4, 1988. p. 991-994.
The natural time series f_oF_2, F10.7, and AE are analyzed and low-dimensional attractors are found, characterized by the correlation dimension and the lower bound of the Kolmogorov entropy. Sources of noise in natural time series are discussed and the concept of extended systems is introduced and used to explain
why the number of data required to calculate the correlation dimension of natural time series is higher than that reported by other authors.