The Mercier criterion is a criterion for plasma used in the theoretical study of plasma instability. It was first proposed in 1954 by C. Mercier, who applied the perturbation method (in which ω ω = ∂ ∂ ∂ ∂ t represents the frequency and k = ∂ ∂ ∂ ∂ z is the z-direction of the unit vector) to the plasma mathematical model to compute calculations.