$$Date:
2015-10-12 12:00:00 -0600 (Mon, 12 Oct 2015)
$$

Abstract

The Seed_Magnetic_Fields thorn seeds magnetic fields into an initial hydrodynamic configuration. Currently seeding into TOV stars is supported, according to the poloidal magnetic field prescription:

$$\begin{array}{rcll}{A}_{x}& =& -y\ast {A}_{b}\ast pow\left(MAX\left(P-{P}_{c}ut,0.0\right),{n}_{s}\right)& \text{(1)}\text{}\text{}\\ {A}_{y}& =& x\ast {A}_{b}\ast pow\left(MAX\left(P-{P}_{c}ut,0.0\right),{n}_{s}\right)& \text{(2)}\text{}\text{}\\ {A}_{z}& =& 0& \text{(3)}\text{}\text{}\\ Phi& =& 0& \text{(4)}\text{}\text{}\end{array}$$

as specified in Appendix B of the IllinoisGRMHD code announcement paper:

http://arxiv.org/pdf/1501.07276.pdf

Note that we must be careful if ${A}_{i}$’s are staggered. In this case, the pressure must be interpolated to the staggered point, and the values of $x$ and $y$ must also be shifted.

Both staggered and unstaggered vector potential fields are currently supported in this thorn.

a_b | Scope: restricted | REAL |

Description: Magnetic field strength parameter.
| ||

Range | Default: 1e-3 | |

*:* | Any real
| |

afield_type | Scope: restricted | KEYWORD |

Description: A-field prescription
| ||

Range | Default: Pressure_prescription | |

see [1] below | A_phi propto (P - P_cut)n̂_s
| |

see [1] below | A_phi propto rho
| |

[1]

Pressure\_prescription

[1]

Density\_prescription

enable_illinoisgrmhd_staggered_a_fields | Scope: restricted | BOOLEAN |

Description: Define A fields on an IllinoisGRMHD staggered grid
| ||

Default: yes | ||

enable_varpi_squared_multiplication | Scope: restricted | BOOLEAN |

Description: Multiply A_phi by varpi2̂?
| ||

Default: yes | ||

n_s | Scope: restricted | REAL |

Description: Magnetic field strength pressure exponent.
| ||

Range | Default: 1.0 | |

*:* | Any real
| |

p_cut | Scope: restricted | REAL |

Description: Cutoff pressure, below which vector potential is set to zero. Typically set to 4% of
the maximum initial pressure.
| ||

Range | Default: 1e-5 | |

0:* | Positive
| |

rho_cut | Scope: restricted | REAL |

Description: Cutoff density, below which vector potential is set to zero. Typically set to 20% of
the maximum initial density.
| ||

Range | Default: 0.2 | |

0:* | Positive
| |

Implements:

seed_magnetic_fields

Inherits:

grid

admbase

hydrobase

This section lists all the variables which are assigned storage by thorn WVUThorns/Seed_Magnetic_Fields. Storage can either last for the duration of the run (Always means that if this thorn is activated storage will be assigned, Conditional means that if this thorn is activated storage will be assigned for the duration of the run if some condition is met), or can be turned on for the duration of a schedule function.

Always: | |

HydroBase::rho[1] HydroBase::press[1] HydroBase::eps[1] HydroBase::vel[1] HydroBase::Bvec[1] HydroBase::Avec[1] HydroBase::Aphi[1] | |

CCTK_INITIAL

seed_magnetic_fields

set up seed magnetic field configuration.

After: | hydrobase_initial | |

Before: | illinoisgrmhd_id_converter | |

Language: | c | |

Type: | function | |