Jakobus A. le Roux
Dept. of Space Science, and Center of Space Plasma & Aeronomic Research (CSPAR), University of Alabama in Huntsville
Anomalous Diffusive Transport and Acceleration of Energetic Particles interacting with Dynamic Small-Scale Magnetic Flux Rope Structures in the Large-scale Solar Wind
Evidence is mounting that the intermittent turbulent nature in the solar wind can partly be explained because small-scale magnetic flux ropes (SMFRs), as part of a non-propagating quasi-2D MHD turbulence component, have a strong presence in the inner heliosphere, as has been predicted for many years. The PDF of the magnetic field component increments of these nonlinear structures is characterized by non-Gaussian power-law statistics with strong tails generated by abrupt SMFR boundaries separated by secondary small-scale current sheets. By implication, induced or motional electric field components are expected to have the same statistical features. Thus, there is good reason to think that energetic particles interacting with SMFRs in the solar wind should exhibit disturbed particle trajectories displaying non-Gaussian power-law statistics. This should result in anomalous diffusive energetic particle transport on intermediate time scales when particles follow magnetic field lines with a transition to normal diffusive behavior at later times. In this talk I will present newly developed focused and Parker-type tempered fractional diffusion-advection equations derived from first principles that model the anomalous diffusive propagation and energization of energetic particles in a dynamic SMFR field on intermediate time scales as well as the later time transition to more normal diffusive states. I will discuss explorative solutions of the fractional Parker transport equation to investigate (1) superdiffusive shock acceleration of energetic particles at a parallel shock imbedded in a SMFR field, and (2) acceleration of energetic particles by dynamic SMFRs when both parallel spatial transport and acceleration are time-fractional superdiffusive processes.