Random walk of magnetic lines of force in astrophysics

We point out the importance of the random fluctuations in astrophysical magnetic fields, which lead among other things to rapid diffusion of energetic particles across the average magnetic field. Application to the interplanetary magnetic field leads to a theory in which the field-line random walk, measured by the observed power spectrum of field fluctuations, is in agreement with that deduced from the observed turbulent motions in the solar photosphere. The two determinations agree well with the recently observed spread in longitude of low-energy particles released at the sun.