Greifswald 2024 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
EP: Fachverband Extraterrestrische Physik
EP 5: Astrophysics
EP 5.2: Vortrag
Mittwoch, 28. Februar 2024, 14:30–14:45, ELP 1: HS 1.22
Lévy flight model for the superdiffusive transport and acceleration of particles at shocks* — •Sophie Aerdker1,2, Lukas Merten1,2, Frederic Effenberger1,2, and Horst Fichtner1,2 — 1Theoretical Physics IV, Faculty of Physics and Astronomy, Ruhr University Bochum — 2Ruhr Astroparticle and Plasma Physics Center (RAPP Center), Germany
In the heliosphere, power laws in space and time profiles of energetic particles at shock fronts are observed. It has been proposed that they result from superdiffusive transport, which can be modelled by Lévy flights. Such anomalous, non-Gaussian, transport regimes may arise as a consequence of intermittent magnetic field structures.
Superdiffusive particle transport can be described by a space-fractional Fokker-Planck equation. Numerical solutions can be obtained by solving the corresponding Stochastic Differential Equations (SDEs). In contrast to Gaussian diffusion, where the SDE is driven by a normal distribution, for superdiffusion random numbers are drawn from a symmetric alpha-stable Lévy distribution.
We investigate particle transport and acceleration at a shock front and use the SDE approach to solve the space-fractional Fokker-Planck equation. With a modified version of CRPropa3.2 the time-dependent solutions of the number density and energy spectrum at the shock are obtained. Our simulations lead to results that are compatible with the expected power-law particle distribution upstream of a shock. We also find slightly flatter energy spectra at the shock, analogously to previous work on Lévy walks. *Supported by DFG (SFB1491)
Keywords: Anomalous diffusion; Diffusive Shock Acceleration; Lévy Flights; Shocks; Stochastic Differential Equations