The origin of the
low-frequency spectrum of fluctuations observed in the solar wind is discussed. It is suggested that this spectrum arises due to sampling random perturbations produced at the Sun. The perturbation process is characterized by a power-law distribution. It is pointed out that, due to solar rotation, the sampling is equivalent to scanning across different size scales on the Sun. The limits of the spectrum found from the observations are used to estimate the characteristic scales on the Sun, the scales related to the origin of the solar wind.