Power spectra and multifractal structure of the intensity fluctuations in the solar photosphere

We analyze the scaling properties of the intensity fluctuations in the solar photosphere. This analysis is based on monochromatic and white light images obtained at the THEMIS telescope with the Italian Panoramic Monochromator. We compute power spectra of the intensity fluctuations, showing that these spectra decrease with a power law with an exponent close to -17/3 in the range of scales smaller than 1.5 Mm. We also analyze the height dependence of the multifractal structure of the "dissipation" fields obtained from the intensity fields, in analogy with the dissipation of passive scalars in turbulent fluids. We show that in the higher photosphere the dissipation field become more intermittent and that it is characterized by more singular structures.