# Elsasser Number

The Elsasser Number is a dimensionless number used in magnetohydrodynamics to describe the relative balance of Lorentz forces to Coriolis forces.

$\Lambda=\frac{\sigma B^2}{\rho\Omega}$

where:
σ is the electrical conductivity of the fluid,
B is the typical magnetic field strength within the fluid,
ρ is the fluid density,
Ω is the angular velocity of the Earth,

A typical value for the Earth is Λ ~ 1[1] .

## References

1. ^ Gubbins, D. (2007), Geodynamo, dimensional analysis and timescales, in Encyclopedia of Geomagnetism and Paleomagnetism, edited by D. Gubbins and E. Herrero-Bervera, pp. 297–300, Springer, Dordrecht.