This is a simple user's and developer's manual for OSHUN.

OSHUN is a fully parallel Vlasov-Fokker-Planck-Maxwell code [1,2] that relies on an arbitrary-order Spherical Harmonic expansion of the distribution function in 3D momentum space. This enables modeling of significant anisotropies in the distribution function e.g. those in two-stream instabilities. The expansion is truncated such that the necessary angular resolution of the distribution function is retained for a given problem. Finite collisionality causes rapid decay of the high-order harmonics, thereby providing a natural truncation mechanism for the expansion.

The fields and configuration space are defined over a 1D or 2D Cartesian grid. (There are minor differences in the way the 1D and 2D code work so they're left as separate entities.). The Vlasov equation is treated in a fully relativistic fashion.

The Fokker-Planck operator is non-relativistic and linearized. The effect of electron-electron collisions on the isotropic component of the distribution can be calculated explicitly or implicitly while electron-ion and electron-electron collisions are treated implicitly for the anisotropic components of the distribution function.

The code has both fully explicit and implicit field-solvers and assumes an infinitely massive and cold ion background.

OSHUN has been benchmarked against recovering transport coefficients in magnetized plasmas.

The normalizations are provided in here.

The way OSHUN determines the time loop from the inputdeck parameters is listed here.

References:

[1] - Tzoufras, M., Bell, A. R., Norreys, P. A., & Tsung, F. S. (2011). A Vlasov-Fokker-Planck code for high energy density physics. Journal of Computational Physics, 230(17), 6475–6494. 10.1016/j.jcp.2011.04.034

[2] - Tzoufras, M., Tableman, A., Tsung, F. S., Mori, W. B., & Bell, A. R. (2013). A multi-dimensional Vlasov-Fokker-Planck code for arbitrarily anisotropic high-energy-density plasmas. Physics of Plasmas, 20(5), 056303. 10.1063/1.4801750

Since the manual is generated by Doxygen, it also contains technical information about the code.

Acknowledgements:

C++ Mathematical Expression Toolkit Library by Arash Partow - http://www.partow.net/programming/exprtk/index.html