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## Functionality overview
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#### Physics system
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NIRVANA is a multi-physics, multi-species, multi-scale simulation code.
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It implements the following physics system:
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... | ... | @@ -116,6 +118,34 @@ assumed edge-centered analog to the electric field. |
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*Note: The TESTFIELDS infrastructure does not implement any numerical
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method to solve induction equations for testfield fluctuations.*
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#### The Boris correction
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NIRVANA supports the so-called Boris correction for reducing the Alfven speed,
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avoiding a too small timestep in MHD simulations with strong magnetic field
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and/or extremely low gas density.
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See the physics guide
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([PDF](https://gitlab.aip.de/ziegler/NIRVANA/-/tree/master/doc/pdf/PhysicsGuide.pdf)).
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for more information on the underlying idea and equations.
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The use of the Boris correction is controlled
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by setting corresponding macros in the user interface
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[nirvanaUser.h](3.2-User-interfaces#user-controllable-macros)).
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#### Magnetic field splitting
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NIRVANA implements a magnetic field splitting strategy. In this strategy the
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magnetic field is decomposed into an imposed background field and a residual field.
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By solving for the (presumably weaker) residual field accuracy of the solution
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can be increased since the background field is discarded
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in the time evolution of the total energy density.
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For details on the modified MHD equations which are solved consult the
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physics guide
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([PDF](https://gitlab.aip.de/ziegler/NIRVANA/-/tree/master/doc/pdf/PhysicsGuide.pdf)).
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Use of the magnetic field splitting is controlled
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by setting the corresponding macro in the user interface
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[nirvanaUser.h](3.2-User-interfaces#user-controllable-macros)
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and by the definition of the background magnetic field in the user interface
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[sourceB0User.c](3.2-User-interfaces#user-defined-background-magnetic-field)).
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## Dynamic arrays
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The NIRVANA infrastructure implements its own proprietary routines for
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PREV: [2 Getting started](2-Getting-started) NEXT: [3.2 User interfaces](3.2-User-interfaces) |
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\ No newline at end of file |
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PREV: [2 Getting started](2-Getting-started) NEXT: [3.2 User interfaces](3.2-User-interfaces) |