The '''Elsasser number''', Λ, is a dimensionless number in magnetohydrodynamics that represents the ratio of magnetic forces to the Coriolis force.{{sfnp|Gubbins|Herrero-Bervera|2007| p=299}}
<math display="block">\Lambda = \frac{\sigma B^2}{\rho \Omega}</math>
where σ is the conductivity of the fluid, ''B'' is the magnetic field, ρ is the density of the fluid, and Ω is the rate of rotation of the body.
== Applications == This number is useful when studying the linear stability of an accretion disc to the magnetorotational instability.<ref>{{Cite journal |last=Lesur |first=Geoffroy R. J. |date=February 2021 |title=Magnetohydrodynamics of protoplanetary discs |url=https://www.cambridge.org/core/journals/journal-of-plasma-physics/article/magnetohydrodynamics-of-protoplanetary-discs/0557575DE812AAA9DD8324A5E6F6165A |journal=Journal of Plasma Physics |language=en |volume=87 |issue=1 |pages=205870101 |doi=10.1017/S0022377820001002 |issn=0022-3778|arxiv=2007.15967 }}</ref>
== Notes == {{Reflist}}
== References == * {{citation | last1 = Gubbins | first1 = David | last2 = Herrero-Bervera | first2 = Emilio | editor-first1 = David | editor-first2 = Emilio | editor-last1 = Gubbins | editor-last2 = Herrero-Bervera | title = Encyclopedia of geomagnetism and paleomagnetism | publisher = Springer | year = 2007 | doi = 10.1007/978-1-4020-4423-6 | isbn = 978-1-4020-3992-8 }}
{{Dimensionless numbers in fluid mechanics}} {{Fluiddynamics-stub}}
Category:Dimensionless numbers of fluid mechanics