The linear growth rate ${\displaystyle \gamma }$  of the RBM instability is given as

${\displaystyle \gamma ^{2}=-{\vec {g_{eff}}}\cdot {\frac {\nabla p}{p}}}$ 

where ${\displaystyle |\nabla p|\sim {\frac {p}{L_{p}}}}$  is the pressure gradient ${\displaystyle g_{eff}=c_{s}^{2}|{\frac {\nabla B}{B}}|\sim 1/R_{0}}$  is the effective gravity produced by a non-homogeneous magnetic field, R₀ is the major radius of the device, L_p is a characteristic length of the pressure gradient, and c_s is the plasma sound speed.

The RBM instability is similar to the Rayleigh–Taylor instability (RT), with Earth gravity ${\displaystyle {\vec {g}}}$  replaced by the effective gravity ${\displaystyle {\vec {g}}_{eff}}$ , except that for the RT instability, ${\displaystyle {\vec {g}}}$  acts on the mass density ${\displaystyle \rho }$  of the fluid, whereas for the RBM instability, ${\displaystyle {\vec {g}}_{eff}}$  acts on the pressure ${\displaystyle p}$  of the plasma.