Observations of anomalous transport of energetic electrons in the heliosphere
08 Jul 2008
Department of Physics, University of Calabria, Ponte P. Bucci, Cubo 31C, 87036, Arcavacata di Rende, Italy
Abstract. We study the propagation of energetic particles, accelerated by interplanetary shock waves, upstream of the shock, considering the possibility of having anomalous transport. The theoretical treatment of the anomalous transport is developed via the propagator formalism, considering that in the case of a superdiffusive transport the propagator has power law tails with slope 2<μ<3, while for a ballistic transport it is approximately constant for small displacements and has a spike for r ≃ vt. Analyzing a data set from Ulysses spacecraft in the period between July 1992 and November 1993, we find that the time profile of electrons accelerated at a traveling planar shock is a power law rather than an exponential decay, implying superdiffusive motion. We also show that the propagator formalism allows to describe the scatter-free propagation, possible for electrons accelerated in impulsive solar events and observed by WIND. These results indicate that the propagation of energetic particles in the turbulent environment of the solar wind can be anomalous, in agreement with the results of recent numerical simulations, and promise to have application to the propagation of particles throughout the heliosphere.