# 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(), 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')
```