Q335 : Computing Magnetic Fields in MALZ

Question
How can I compute magnetic fields with the MALZ program?

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Answer
First, the magnetic field computation option must be turned on. This is done by selecting either "Magnetic Fields" or "Both" under Compute in the Computations screen of MALZ.

The specification of observation points for the computation of magnetic fields in MALZ is somewhat indirect. First, the magnetic fields can only be computed in the air or at the air-soil interface. On the other hand, you can't specify the observation points to be in the air: the program will only allow the specification of observation points that are either buried in the earth or at the earth's surface. To specify the height above ground at which the observation points for the computation of magnetic fields should be located, you have to specify an "Offset". This can be set in the Compute frame of the 'MALZ | Computations' screen. For the purpose of computation of magnetic fields, this offset will be added to the Z coordinate of all observation points.

This arrangement allows you to compute simultaneously the earth potentials at observation points that are either buried or at the earth's surface and the magnetic field at points located at a fixed distance, directly above those observation points.

Note that the direction of positive Z is down into the earth in MALZ, which means that observation points in the air should always be located at negative or zero coordinates. In particular, this means that the 'Offset' should also normally be negative.

For example, if the observation points are located at 1 m in the ground and you want to study the magnetic fields at 1 m above the ground, an Offset of -2 must be specified.

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