# geoana.em.static.LineCurrentFreeSpace.magnetic_flux_density#

LineCurrentFreeSpace.magnetic_flux_density(xyz)#

Compute the magnetic flux density for the static current-carrying wire segments.

Parameters:
xyz(n, 3) numpy.ndarray xyz

gridded locations at which we are calculating the magnetic flux density

Returns:
(n, 3) numpy.ndarray

The magnetic flux density at each observation location in T.

Examples

Here, we define a horizontal square loop and plot the magnetic flux density on the XZ-plane that intercepts at Y=0.

```>>> from geoana.em.static import LineCurrentFreeSpace
>>> from geoana.utils import ndgrid
>>> from geoana.plotting_utils import plot2Ddata
>>> import numpy as np
>>> import matplotlib.pyplot as plt
```

Let us begin by defining the loop. Note that to create an inductive source, we closed the loop

```>>> x_nodes = np.array([-0.5, 0.5, 0.5, -0.5, -0.5])
>>> y_nodes = np.array([-0.5, -0.5, 0.5, 0.5, -0.5])
>>> z_nodes = np.zeros_like(x_nodes)
>>> nodes = np.c_[x_nodes, y_nodes, z_nodes]
>>> simulation = LineCurrentFreeSpace(nodes)
```

Now we create a set of gridded locations and compute the magnetic flux density.

```>>> xyz = ndgrid(np.linspace(-1, 1, 50), np.array([0]), np.linspace(-1, 1, 50))
>>> B = simulation.magnetic_flux_density(xyz)
```

Finally, we plot the magnetic flux density on the plane.

```>>> fig = plt.figure(figsize=(4, 4))
>>> ax = fig.add_axes([0.15, 0.15, 0.8, 0.8])
>>> plot2Ddata(xyz[:, [0, 2]], B[:, [0, 2]], ax=ax, vec=True, scale='log', ncontour=25)
>>> ax.set_xlabel('X')
>>> ax.set_ylabel('Z')
>>> ax.set_title('Magnetic flux density')
```