Time-step Considerations in Particle Simulation Algorithms for Coulomb Collisions in Plasmas
The accuracy of first-order Euler and higher-order time-integration algorithms for grid-based Langevin equations collision models in a specific relaxation test problem is assessed. We show that statistical noise errors can overshadow time-step errors and argue that statistical noise errors can be conflated with time-step effects. Using a higher-order integration scheme may not achieve any benefit in accuracy for examples of practical interest. We also investigate the collisional relaxation of an initial electron-ion relative drift and the collisional relaxation to a resistive steady-state in which a quasi-steady current is driven by a constant applied electric field, as functions of the time step used to resolve the collision processes using binary and grid-based, test-particle Langevin equations models. We compare results from two grid-based Langevin equations collision algorithms to results from a binary collision algorithm for modeling electronion collisions. Some guidance is provided regarding how large a time step can be used compared to the inverse of the characteristic collision frequency for specific relaxation processes.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 988953
- Report Number(s):
- LLNL-JRNL-419386; ITPSBD; TRN: US1006997
- Journal Information:
- IEEE Transactions on Plasma Science, Vol. 38, Issue 9 Pt 1; ISSN 0093-3813
- Country of Publication:
- United States
- Language:
- English
Similar Records
Higher-order time integration of Coulomb collisions in a plasma using Langevin equations
A hybrid method for hydrodynamic-kinetic flow Part I: A particle-grid method for reducing stochastic noise in kinetic regimes