  We use multifractal detrended fluctuation analysis (MF-DFA), to See query 1
study sunspot number fluctuations. The result of the MF-DFA shows that there
are three crossover timescales in the fluctuation function. We discuss how the
existence of the crossover timescales is related to a sinusoidal trend. Using
Fourier detrended fluctuation analysis, the sinusoidal trend is eliminated. The
Hurst exponent of the time series without the sinusoidal trend is $0.12\pm
0.01$. Also we find that these fluctuations have multifractal nature. Comparing
the MF-DFA results for the remaining data set to those for shuffled and
surrogate series, we conclude that its multifractal nature is almost entirely
due to long range correlations.
