Resistive ballooning mode

The resistive ballooning mode (RBM) is an instability occurring in magnetized plasmas, particularly in magnetic confinement devices such as tokamaks, when the pressure gradient is opposite to the effective gravity created by a magnetic field.
Linear growth rate.
The linear growth rate formula_1 of the RBM instability is given as
where formula_3 is the pressure gradient formula_4 is the effective gravity produced by a non-homogeneous magnetic field, "R"0 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.
Similarity with the Rayleigh–Taylor instability.
The RBM instability is similar to the Rayleigh–Taylor instability (RT), with Earth gravity formula_5 replaced by the effective gravity formula_6, except that for the RT instability, formula_5 acts on the mass density formula_8 of the fluid, whereas for the RBM instability, formula_6 acts on the pressure formula_10 of the plasma.