Gauss (unit)

The gauss, symbol G (sometimes Gs), is a unit of measurement of magnetic induction, also known as magnetic flux density. The unit is part of the Gaussian system of units, which inherited it from the older CGS-EMU system. It was named after the German mathematician and physicist Carl Friedrich Gauss in 1936. One gauss is defined as one maxwell per square centimetre. As the cgs system has been superseded by the International System of Units (SI), the use of the gauss has been deprecated by the standards bodies, but is still regularly used in various subfields of science. The SI unit for magnetic flux density is the tesla (symbol T), which corresponds to 10,000 gauss. Albeit not a component of the International System of Units, the usage of the gauss generally follows the rules for SI units. Since the name is derived from a person's name, its symbol is the uppercase letter G. When the unit is spelled out, it is written in lowercase ("gauss"), unless it begins a sentence. The gauss may be combined with metric prefixes, such as in milligauss, mG (or mGs), or kilogauss, kGauss or kG. The gauss is the unit of magnetic flux density B in the system of Gaussian units and is equal to Mx/cm2 or g/Bi/s2, while the oersted is the unit of H-field. One tesla (T) corresponds to 104 gauss, and one ampere (A) per metre corresponds to 4π × 10−3 oersted. The units for magnetic flux Φ, which is the integral of magnetic B-field over an area, are the weber (Wb) in the SI and the maxwell (Mx) in the CGS-Gaussian system. The conversion factor is e8maxwell per weber, since flux is the integral of field over an area, area having the units of the square of distance, thus e4G/T (magnetic field conversion factor) times the square of e2cm/m (linear distance conversion factor). 108 Mx/Wb = 104 G/T × (102 cm/m)2. Orders of magnitude (magnetic field) 10−9–10−8 G – the magnetic field of the human brain 10−6–10−3 G – the magnetic field of Galactic molecular clouds. Typical magnetic field strengths within the interstellar medium of the Milky Way are ~5 μG.