An important topic in space research is represented by the study of statistical properties of the interplanetary magnetic field fluctuations, these being closely related to acceleration processes and energy transport in the solar wind. Analysis of the probability distribution functions of the velocity and magnetic field fluctuations has underlined their non‐Gaussian properties on small time scales, and uncorrelated features at large scale. In this paper, numerical solutions of space‐time fractional diffusion equations are used to analyze the presence or absence of heavy tails typically associated with multiscale behavior, in the case of the interplanetary magnetic field data obtained by Ulysses mission.