milligauss

Milligauss is a unit of magnetic flux density in the centimetre–gram–second (CGS) gauss system, defined as one thousandth of a gauss. In SI units it corresponds to 1 × 10^-7 tesla. Equivalently, 1 milligauss equals 0.1 microtesla or 100 nanotesla. The term is commonly used in contexts where magnetic fields are relatively weak, such as geophysics and paleomagnetism, and in some laboratory measurements.

Typical uses and magnitudes: The Earth's magnetic field at the surface is usually in the range of about 0.25 to 0.65 gauss, or roughly 250 to 650 milligauss, depending on location. In laboratory or specialized measurements, fields may span from milligauss to several gauss or more, but milligauss denotes relatively weak, ambient, or background levels. In SI terms, many modern instruments report in tesla or microtesla, with 1 milligauss equal to 0.1 microtesla or 100 nanotesla.

Measurement and instruments: Milligauss values are obtained with magnetometers such as fluxgate sensors, optically pumped magnetometers, or SQUID-based devices, depending on the required sensitivity. Measurements require proper calibration and shielding to avoid interference from nearby electrical devices and ferromagnetic materials. While SI usage has favored tesla and microtesla, milligauss remains a common unit in older literature and in certain geophysical and astrophysical contexts.

Related units: Gauss (G) and tesla (T) are the primary units for magnetic flux density, with 1 G = 10^-4 T and 1 T = 10^4 G. 1 mG = 0.1 µT = 100 nT.