Gauss (unit)
Template:Short description Template:Infobox unit
The gauss (symbol: Template:Val, 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 centimetre–gram–second electromagnetic units (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As the centimetre–gram–second system of units (cgs system) has been superseded by the International System of Units (SI), the use of the gauss has been deprecated by the standards bodies, but is still regularly used in various subfields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, and preferred in astrophysics.<ref>J. B. Zirker, The Magnetic Universe., Johns Hopkins University Press, Baltimore, 2009, p. 281.</ref> The SI unit for magnetic flux density is the tesla (symbol T),<ref>NIST Special Publication 1038, Section 4.3.1</ref> which corresponds to Template:Gaps.
Name, symbol, and metric prefixes
Although 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.<ref name="SIBrochure9thEd">Template:SIbrochure9th</ref>Template:Rp The gauss may be combined with metric prefixes,<ref name="SIBrochure8th">Template:SIbrochure8th</ref>Template:Rp such as in milligauss, mG (or mGs), or kilogauss, kG (or kGs).
Unit conversions
<math display="block">\begin{align} 1\,{\rm G} &= {\rm Mx}{\cdot}{\rm cm}^{-2} = \frac{\rm g}{{\rm Bi}{\cdot}{\rm s}^2}\\
&\text{ ≘ } 10^{-4}\,{\rm T} = 10^{-4}\frac{\rm kg}{{\rm A}{\cdot}{\rm s^2}}
\end{align}</math>
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 [[Magnetic_field#The_H-field|Template:Math-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_field#The_B-field|magnetic Template:Math-field]] over an area, are the weber (Wb) in the SI and the maxwell (Mx) in the CGS-Gaussian system. The conversion factor is Template:Val, since flux is the integral of field over an area, area having the units of the square of distance, thus Template:Val (magnetic field conversion factor) times the square of Template:Val (linear distance conversion factor). 108 Mx/Wb = 104 G/T × (102 cm/m)2.
Typical values
- 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.
- 0.25–0.60 G – the Earth's magnetic field at its surface
- 4 G – near Jupiter's equator
- 25 G – the Earth's magnetic field in its core<ref name="buff2010">Buffett, Bruce A. (2010), "Tidal dissipation and the strength of the Earth's internal magnetic field", Nature, volume 468, pages 952–954, Template:Doi</ref>
- 50 G – a typical refrigerator magnet
- 100 G – an iron magnet
- 1500 G – within a sun spot<ref>Template:Cite web</ref>
- 10000 to 13000 G – remanence of a neodymium-iron-boron (NIB) magnet<ref>Template:Cite book</ref>
- 16000 to 22000 G – saturation of high permeability iron alloys used in transformers<ref>Template:Cite book</ref>
- 3000–70000 G – a medical magnetic resonance imaging machine
- 1012–1013 G – the surface of a neutron star<ref>Template:Cite web</ref>
- 4 × 1013 G – the Schwinger limit
- 1014 G – the magnetic field of SGR J1745-2900, orbiting the supermassive black hole Sgr A* in the center of the Milky Way.
- 1015 G – the magnetic field of some newly created magnetars<ref name="sciam_article">Template:Cite web</ref>
- 1017 G – the upper limit to neutron star magnetism<ref name="sciam_article" />