# Software - GISMO

Magentized plasmas in the interstellar medium and the heliosphere exhibit turbulence over large Wave number ranges. The transport of energetic particles happens through shock-free interaction with this turbulence.

It is widely assumed that the turbulence is described by incompressible magnetohydrodynamics. Which turbulence model applies in this description is still being discussed. From Kolmogorov across Kraichnan-Iroshnikov to Goldreich-Sridhar there are many options.

An investigation of the turbulence is ultimately only possible with numerical methods. Here was the GISMO code from us developed which delivers a pseudo-spectral solution of the incompressible MHD equation and this with the movement charged test particles combined.

GISMO solves the MHD equations in the Elsässer notation. The Fourier transformation is performed with the p3dfft library. This makes MPI parallelization possible, which is easily done on many 1000 cores. Output for fields and particles is solved via HDF5. The scheme of a time step is in Image shown below.

* Schematic sequence of the
GISMO codes: The areas for MHD development (left) and particle development (right) are recognizable. Quantities
in Fourier space are blue, quantities in real space are orange. The real space fields are at one point passed to
the particle code. Since these are test particles, there is no reaction. *

The code and its application are discussed in Evolution of plasma turbulence excited with particle beams (Lange and Spanier 2012, Astronomy and Astrophysics) and Particle scattering in turbulent plasmas with amplified wave modes (Lange, Spanier, Battarbee, Vainio and Laitinen 2013, Astronomy and Astrophysics) . Scientific results are available at Research / Transport described.

The code is not freely available. Collaborations are possible on request.