F. Lepreti et al., Persistence of solar activity on small scales: Hurst analysis of time series coming from H alpha flares, SOLAR PHYS, 197(1), 2000, pp. 149-156
We calculated the Hurst exponent H for the daily averaged intensity Q of op
tical flares, an index which describes the solar activity. We found that H
similar or equal to0.74 +/-0.02 in the range of scales from about 20 days u
p to 450 days. This value is well beyond H=1/2, expected for a stochastic B
rownian process, thus indicating that the solar cycle could show persistenc
e on small scales, in agreement with what has been found using other indice
s of the solar cycle.