Time-step considerations in particle simulation algorithms for coulomb collisions in plasmas

Bruce I. Cohen, Andris M. Dimits, Alex Friedman, Russel E. Caflisch

Research output: Contribution to journalArticlepeer-review


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 electron-ion collisions. Some guidance is provided on how large a time step can be used compared to the inverse of the characteristic collision frequency for specific relaxation processes.

Original languageEnglish (US)
Article number5475281
Pages (from-to)2394-2406
Number of pages13
JournalIEEE Transactions on Plasma Science
Issue number9 PART 1
StatePublished - Sep 2010


  • Algorithms
  • collision processes
  • computer applications
  • numerical analysis
  • particle collisions
  • plasmas

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Condensed Matter Physics


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