# Ekman Number

The Ekman Number is a dimensionless number used is geophysics to describe the relative balance of viscous forces to Coriolis forces in the fluid outer core.

$E_k=\frac{\nu}{2\Omega r_0^2}$

where:
ν is the kinematic viscosity of the fluid,
Ω is the angular velocity of the Earth,
r0 is the radius of the fluid core.

A typical value for the Earth is Ek ~ 10-9[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.