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Research | Space Research | Space Plasma Physics - Numerical simulations
Interaction between Solar Wind and Earth magnetic field
Numerical GUMICS-3 simulation (FMI)
Numerical simulations
Numerical simulations of space plasmas are either particle simulations, fluid simulations or hybrids of the two approaches. In case of hybrid simulations, electrons are usually treated as a fluid while ions are particles.
In particle simulations, the trajectories of a large number of electrons and ions are numerically integrated forward in time under the electric or electromagnetic fields generated by the particles themselves. The number of particles in the simulation, although large (typically one million), is never anywhere as large as in Nature. Therefore, each (macro)particle in the simulation represents many physical particles. The drawback of particle simulations is particle noise which limits the accuracy of the results. Particle simulations are typically used to study small scale phenomena.
In fluid simulations the plasma is treated as a magnetized fluid (magnetohydrodynamics, MHD). This approximation ignores kinetic effects, that is, any nontrivial structures in particle velocity distribution are ignored. It is valid for large-scale phenomena at least, such as modelling the whole magnetosphere. Generally, fluid simulations are used whenever applicable because of their superior computational performance compared with particle simulations.
The GUMICS-3 model is a global MHD simulation coupled with a comprehensive ionospheric model, developed at the Geophysical Research Division of Finnish Meteorological Institute..
A still unsolved question in MHD simulations is how to write a scheme which never produces negative pressures while being fully conservative and preventing spurious magnetic monopoles from occurring. Particle simulations do not, by construction, produce negative pressures.
More information:
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