How can Helmholtz coils reduce the effect of Earth’s magnetic field in an experiment?

A Helmholtz coil consists of two equal, parallel, coaxial circular coils separated by a distance equal to their radius. This specific configuration produces a magnetic field in the central region between the coils that is homogeneous to a remarkably high degree.12

To reduce or cancel the effect of Earth’s magnetic field during an experiment, researchers can carefully orient the Helmholtz coil and adjust the current flowing through it. By generating an opposing magnetic field of equal magnitude, the device can effectively neutralize the geomagnetic field within the central region, creating a space where experiments can be conducted in the absence of external magnetic interference.2