Particle propagation in the solar wind: Anomalous diffusion of magnetic field lines in turbulent magnetic fields

Abstract

In order to predict the entry of energetic particles of solar origin into the Earth's magnetosphere, it is necessary to understand how these particles propagate in the solar wind. The random walk of magnetic field lines is studied numerically in the case that a spectrum of magnetic fluctuations is present. In particular, the anisotropic turbulence typical of the solar wind is simulated by varying the spectral parameters. We find that transport of magnetic field lines, and therefore of energetic particles, is anomalous, that is, superdiffusion or subdiffusion can occur in the plane normal to the background magnetic field. Superdiffusion is found in the direction normal to the ecliptic plane. This implies that even particles accelerated at high solar latitude, can reach the Earth and penetrate the magnetosphere.