Time-Domain EM (simpeg.electromagnetics.time_domain)#

The time_domain module contains functionality for solving Maxwell’s equations in the time-domain for controlled sources. Here, electric displacement is ignored, and functionality is used to solve:

\[\begin{split}\begin{align} \nabla \times \vec{e} + \frac{\partial \vec{b}}{\partial t} &= -\frac{\partial \vec{s}_m}{\partial t} \\ \nabla \times \vec{h} - \vec{j} &= \vec{s}_e \end{align}\end{split}\]

where the constitutive relations between fields and fluxes are given by:

  • \(\vec{j} = \sigma \vec{e}\)

  • \(\vec{b} = \mu \vec{h}\)

and:

  • \(\vec{s}_m\) represents a magnetic source term

  • \(\vec{s}_e\) represents a current source term

Simulations#

Simulation1DLayered([survey, time_filter])

Simulation class for simulating the TEM response over a 1D layered Earth for a single sounding.

Simulation3DMagneticFluxDensity(mesh[, ...])

3D TDEM simulation in terms of the magnetic flux density.

Simulation3DElectricField(mesh[, survey, ...])

3D TDEM simulation in terms of the electric field.

Simulation3DMagneticField(mesh[, survey, ...])

3D TDEM simulation in terms of the magnetic field.

Simulation3DCurrentDensity(mesh[, survey, ...])

3D TDEM simulation in terms of the current density.

Receivers#

receivers.PointElectricField([locations, ...])

Measure TDEM electric field at a point.

receivers.PointCurrentDensity([locations, ...])

Measure TDEM current density at a point.

receivers.PointMagneticFluxDensity([...])

Measure TDEM magnetic flux density at a point.

receivers.PointMagneticFluxTimeDerivative([...])

Measure time-derivative of magnetic flux density at a point.

receivers.PointMagneticField([locations, ...])

Measure TDEM magnetic field at a point.

receivers.PointMagneticFieldTimeDerivative([...])

Measure time-derivative of magnet field at a point.

Waveforms#

sources.StepOffWaveform([off_time])

A heavy-side step function waveform.

sources.RampOffWaveform([ramp_start,] ramp_end)

A waveform with a linear ramp-off.

sources.RawWaveform([off_time, ...])

A waveform you can define.

sources.VTEMWaveform([off_time, peak_time, ...])

A VTEM style waveform

sources.TrapezoidWaveform(ramp_on, ramp_off)

A waveform that has a linear ramp-on and a linear ramp-off.

sources.TriangularWaveform(start_time, ...)

TriangularWaveform is a special case of TrapezoidWaveform where there's no pleateau

sources.QuarterSineRampOnWaveform(ramp_on, ...)

A waveform that has a quarter-sine ramp-on and a linear ramp-off

sources.HalfSineWaveform(ramp_on, ramp_off, ...)

A waveform that has a quarter-sine ramp-on and a quarter-cosine ramp-off.

Sources#

sources.MagDipole([receiver_list, location, ...])

Point magnetic dipole source calculated by taking the curl of a magnetic vector potential.

sources.CircularLoop([receiver_list, ...])

Circular loop magnetic source calculated by taking the curl of a magnetic vector potential.

sources.LineCurrent([receiver_list, ...])

Line current source.

sources.RawVec_Grounded([receiver_list, s_e])

Surveys#

survey.Survey(source_list, **kwargs)

Time domain electromagnetic survey

Fields#

Fields3DMagneticFluxDensity(simulation)

Fields class for storing 3D total magnetic flux density solutions.

Fields3DElectricField(simulation)

Fields class for storing 3D total electric field solutions.

Fields3DMagneticField(simulation)

Fields class for storing 3D total magnetic field solutions.

Fields3DCurrentDensity(simulation)

Fields class for storing 3D current density solutions.

Base Classes#

receivers.BaseRx(locations, times[, ...])

Base TDEM receiver class

sources.BaseWaveform([has_initial_fields, ...])

Base class for creating a waveform for time-domain EM simulations.

sources.BaseTDEMSrc([receiver_list, ...])

Base TDEM source class

simulation.BaseTDEMSimulation(mesh[, ...])

Base class for quasi-static TDEM simulation with finite volume.

fields.FieldsTDEM(simulation)

Base class for storing TDEM fields.

fields.FieldsDerivativesEB(simulation)

Field class for stashing derivatives for EB formulations.

fields.FieldsDerivativesHJ(simulation)

Field class for stashing derivatives for HJ formulations.