get_source_field

emg3d.fields.get_source_field(grid, src, freq, strength=0, electric=True, length=1.0, decimals=6, **kwargs)

Return the source field.

The source field is given in Equation 2 in [Muld06],

\[s \mu_0 \mathbf{J}_\mathrm{s} ,\]

where \(s = \mathrm{i} \omega\). Either finite length dipoles, infinitesimal small point dipoles, or arbitrarily shaped segments can be defined, whereas the returned source field corresponds to a normalized (1 Am) source distributed within the cell(s) it resides (can be changed with the strength-parameter).

The adjoint of the trilinear interpolation is used to distribute the point(s) to the grid edges, which corresponds to the discretization of a Dirac ([PlDM07]).

Parameters:

grid : TensorMesh

Model grid; a emg3d.meshes.TensorMesh instance.

src : list of floats

Source coordinates (m). There are three formats:

• Finite length dipole: [x0, x1, y0, y1, z0, z1].
• Point dipole: [x, y, z, azimuth, dip].
• Arbitrarily shaped source: [[x-coo], [y-coo], [z-coo]].

Point dipoles will be converted internally to finite length dipoles of length. In the case of a point dipole one can set electric=False, which will create a square loop of length``x``length perpendicular to the dipole.

freq : float

Source frequency (Hz), used to compute the Laplace parameter s. Either positive or negative:

• freq > 0: Frequency domain, hence \(s = -\mathrm{i}\omega = -2\mathrm{i}\pi f\) (complex);
• freq < 0: Laplace domain, hence \(s = f\) (real).

strength : float or complex, optional

Source strength (A):

• If 0, output is normalized to a source of 1 m length, and source strength of 1 A.
• If != 0, output is returned for given source length and strength.

Default is 0.

electric : bool, optional

Shortcut to create a magnetic source. If False, the format of src must be that of a point dipole: [x, y, z, azimuth, dip] (for the other formats setting electric has no effect). It then creates a square loop perpendicular to this dipole, with side-length 1. Default is True, meaning an electric source.

length : float, optional

Length (m) of the point dipole when converted to a finite length dipole, or edge-length (m) of the square loop if electric=False. Default is 1.0.

decimals: int, optional

Grid nodes and source coordinates are rounded to given number of decimals. Default is 6 (micrometer).

Returns:

sfield : SourceField() instance

Source field, normalized to 1 A m.