astronomix.initial_condition_generation.magnetic_field_from_vector_potential

Construct divergence-free magnetic fields from a vector potential.

Initialising the magnetic field from a vector potential A and taking a discrete curl guarantees div(B) = 0 to machine precision under the matching discrete divergence operator. The correct discretisation of that curl depends on the solver topology, so this module branches on the solver mode: staggered edge-centered differences for the constrained-transport finite-difference scheme, and a central-difference curl for the cell-centered finite-volume scheme.

Module Contents

Functions

setup_magnetic_fields_from_vector_potential

Calculate the cell-centered and face-centered magnetic fields from a given vector potential function, correctly applying discrete curl operations depending on the solver mode (FINITE_DIFFERENCE or FINITE_VOLUME) to ensure a divergence-free magnetic field.

API

astronomix.initial_condition_generation.magnetic_field_from_vector_potential.setup_magnetic_fields_from_vector_potential(config: astronomix.option_classes.simulation_config.SimulationConfig, vector_potential_func: Callable, *args, **kwargs) → Tuple[jax.numpy.ndarray, jax.numpy.ndarray, jax.numpy.ndarray, jax.numpy.ndarray, jax.numpy.ndarray, jax.numpy.ndarray]

Calculate the cell-centered and face-centered magnetic fields from a given vector potential function, correctly applying discrete curl operations depending on the solver mode (FINITE_DIFFERENCE or FINITE_VOLUME) to ensure a divergence-free magnetic field.

Note: Uniform background fields cannot be correctly generated from a periodic vector potential. Add background fields to the returned arrays after calling.

Args:

config: The simulation configuration object. vector_potential_func: A callable f(X, Y, Z, *args, **kwargs) that

returns a tuple (A_x, A_y, A_z) evaluated at the given coordinates.

*args: Additional positional arguments passed to

vector_potential_func (e.g. a time t).

**kwargs: Additional keyword arguments passed to

vector_potential_func.

Returns:

B_x, B_y, B_z: Cell-centered magnetic field components. bxb, byb, bzb: Face-centered (interface) magnetic field components.