Lorentz miniapp documentation #292
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ping: @Zane-Hays |
najlkin
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Oct 8, 2025
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Nice reading, @mlstowell 👍
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| The Lorentz mini application approximates the trajectory of an individual | ||
| particle using the explicit Boris algorithm. The equations being solved track | ||
| the position and momentum of a particle with a given mass and charge. |
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position (x) and momentum (p)...
| \end{align}$$ | ||
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| The Boris algorithm, while not a symplectic method, provides long term accuracy | ||
| by conserving volume in phase space. The algorithm updates the position in a single step but splits the momentum update into multiple steps: |
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line wrap + ... multiple steps between time levels k and k+1
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| While equation \eqref{boris2} may appear to be implicit it is clearly a linear | ||
| equation so a small amount of algebra will produce an explicit, though more | ||
| messy and less intuitive, formula. |
| ### Lorentz Mini Application | ||
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| The Lorentz mini application approximates the trajectory of an individual | ||
| particle using the explicit Boris algorithm. The equations being solved track |
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It could be mentioned it track the particle in provided electric (E) and magnetic (B) fields.
| $$\begin{align} | ||
| \frac{d\vec{x}}{dt} & = \frac{\vec{p}}{m} \\\\ | ||
| \frac{d\vec{p}}{dt} & = | ||
| q\left(\E + \frac{1}{m}\vec{p}\times\B\right) |
| VisItDataCollection is provided. The command line option `-er` can be used | ||
| to set the root name of the data collection e.g. `-er Volta-AMR-Parallel`. | ||
| The field name within the data collection is assumed to be `E` unless | ||
| overridden with `-ef`. The cylce index is assumed to be 10 but this can be |
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Suggested change
| overridden with `-ef`. The cylce index is assumed to be 10 but this can be | |
| overridden with `-ef`. The cycle index is assumed to be 10 but this can be |
| #### Mini Application Features | ||
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| **Electric Field:** The electric field is assumed to be zero unless a | ||
| VisItDataCollection is provided. The command line option `-er` can be used |
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| VisItDataCollection is provided. The command line option `-er` can be used | |
| VisIt data collection is provided. The command line option `-er` can be used |
The user does not provide the MFEM object, but path to data, so should be rather written like this (and also we do not need to care about formatting of the class name)
| index and processor rank can also be overridden if necessary. | ||
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| **Magnetic Field:** The magnetic field is assumed to be zero unless a | ||
| VisItDataCollection is provided. The command line option `-br` can be used |
| VisItDataCollection is provided. The command line option `-br` can be used | ||
| to set the root name of the data collection e.g. `-br Tesla-AMR-Parallel`. | ||
| The field name within the data collection is assumed to be `B` unless | ||
| overridden with `-bf`. The cylce index is assumed to be 10 but this can be |
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| overridden with `-bf`. The cylce index is assumed to be 10 but this can be | |
| overridden with `-bf`. The cycle index is assumed to be 10 but this can be |
| ## Lorentz Miniapp: Particle Trajectory Calculation | ||
| <img class="floatright" src="../img/examples/lorentz.png"> | ||
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| This miniapp reads VisItDataCollection objects produced by applications such as |
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Documentation for mfem/mfem#4567