Wolfgang Droege

Superevents : their origin and propagation through the heliosphere from 0.3 to 35 AU

Superevents are long-lasting enhancements of the interplanetary particle population that are observed initially in the inner heliosphere (≤1 AU) and that propagate to the outer heliosphere (≥35 AU) with speeds of ≃800 km s −1 . Superevents are observed in nuclei at energies up to tens of MeV as well as in MeV electrons and differ distinctly from known intensity increases due to single solar flare particle events, corotating events, and energetic storm particle events

Quasi-linear theory and the phenomenology of interplanetary solar particle transport

The apparent disagreement between the scattering mean free paths as derived empirically from solar particle events and theoretically within the framework of quasi-linear theory from measured magnetic field fluctuation spectra has been a longstanding problem in space plasma physics. This discrepancy has important implications for astrophysics because quasi-linear theory is widely used in cosmic-ray and other energetic particle transport problems. In order to resolve the discrepancy we continue in this Letter earlier work where details of the dispersion relation of waves propagating with respect to the average solar wind flow were taken into account

Ion dynamics in quasi-perpendicular collisionless interplanetary shocks: a case study

Interplanetary shocks are believed to play an important role in the acceleration of charged particles in the heliosphere. While the acceleration to high energies proceeds via the diffusive mechanism at the scales exceeding by far the shock width, the initial stage (injection) should occur at the shock itself. Numerical tracing of ions is done in a model quasi-perpendicular shock front with a typical interplanetary shock parameters (Mach number, upstream ion temperature). The analysis of the distribution of the transmitted solar wind is used to adjust the cross-shock potential which is not directly measured. It is found that, for typical upstream ion temperatures, acceleration of the ions from the tail of the solar wind distribution is unlikely. Pickup ions with a shell distribution are found to be effectively energized and may be injected into further diffusive acceleration regime. Pre-accelerated ions are efficiently upscaled in energies. A part of these ions is returned to the upstream region where they can further be diffusively accelerated.