We present the results of a statistical rescaled range (R/S) analysis of natural electromagnetic noise in the extremely low frequency (ELF) band. The Hurst exponent was derived from the records of two horizontal magnetic antennas taken in Antarctica with a sample frequency of 512 Hz, to guarantee enough resolution with the small number of samples in the analysis. The study shows that ELF radio noise is a persistent random process, maintaining its value between 0.75 and 0.85 for the different series analyzed. A numerical simulation was performed, in which each discharge was modeled by the radiated field of a wire antenna excited by a Gaussian pulse, demonstrating a way of inferring lightning rates from R/S analysis.