Diffusion in a collisional standard map

Area of Science:

• Plasma Physics
• Fusion Energy
• Astrophysical Plasmas

Background:

• Charged particles in magnetized plasmas are influenced by magnetic field fluctuations and collisions.
• Resonant magnetic perturbations (RMPs) can lead to chaotic magnetic field lines, affecting particle transport.
• Understanding particle diffusion is crucial for plasma confinement and understanding astrophysical phenomena.

Purpose of the Study:

• To evaluate the diffusion coefficient of test particles in plasmas with magnetic field fluctuations and binary collisions.
• To investigate the scaling of diffusion beyond quasilinear and subdiffusive behaviors.
• To verify the appearance of the Rechester-Rosenbluth regime and its relation to other diffusion models.

Main Methods:

• Modeling binary collisions using a constant collision frequency.
• Utilizing a collisional Chirikov-Taylor (standard) map to simulate single-particle motion.
• Analyzing diffusion dependence on magnetic perturbation strength and collision frequency.
• Supplementing theoretical estimates with numerical simulations.

Main Results:

• The study confirms the existence of the Rechester-Rosenbluth diffusion regime.
• It is demonstrated that the Kadomtsev-Pogutse diffusion coefficient represents the strong collisional limit of the Rechester-Rosenbluth formula.
• Diffusion scaling beyond quasilinear and subdiffusive behaviors was investigated.

Conclusions:

• The interplay between magnetic field perturbations and collisions significantly impacts particle diffusion.
• The Rechester-Rosenbluth regime is a key feature of particle transport in such systems.
• The findings contribute to a better understanding of particle dynamics in magnetized plasmas relevant to fusion and astrophysics.