  We have proposed a novel application for cosmic-ray muography, called
Magic-$\mu$, which is short for Magnetic field Imaging by Cosmic-ray Muons. The
general goal of Magic-$\mu$ is to detect the presence of a magnetic field or
magnetic flux density whose three-dimensional distribution is unknown.
Depending on the application, Magic-$\mu$ can have three detection modes. The
first is "magnetic field imaging," which is detecting the presence of a
magnetic field in specific voxels within a region of space. The other two
modes, transmission and deflection, aim not only to detect the presence but
also to measure the flux density of the magnetic field. We have performed a
feasibility study using the PHITS Monte Carlo simulation code, for strong and
weak magnetic fields. In this paper, we first give an overview of the concept
and basic principles of magnetic field muography. Then, the results of the
feasibility study on magnetic field imaging for a strong magnetic field (more
than 500 mT) are presented.
