Elsasser number

The Elsasser number, Λ, is a dimensionless number in magnetohydrodynamics that represents the ratio of magnetic forces to the Coriolis force.^[1]

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

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.^[2]