LONG-TERM PERSISTENCE OF SOLAR ACTIVITY

We examine the question of whether or not the non-periodic variations in solar activity are caused by a white-noise random process. ‘l’he IIurst exponent, which characterizes the persistence of a time series, is evaluated for the series of 14L’ data for the time interval from about 6000 IIC to 1950 AD. We find a constant Hurst exponent, suggesting that solar activity in the frequency range of from 100 to 3000 years inclucles an important continuum component in addition to the well known periodic variations. l’he value we calculate, H % 0.8, is significantly larger than the value of 0.5 that would correspond to variations produced by white noise process. This value is in good agreement with the results for the monthly sunspot data reported elsewhere, indicating that the physics that produces the continuum is a correlated random process and that it is the same type of process over a wide range of time interval lengths.