A short remark on Kalaawy's variational principle for plasma

Purpose - This paper aims to show how to establish a variational formulation directly from the governing equations. A modified Burger equation arising in dusty plasma is used as an example to show the derivation process. Design/methodology/approach - Ji-Huan He's semi-inverse method is adopted in the derivation process. To effectively use the semi-inverse method, a potential function is introduced, and the trial functional is constructed with some nonzero parameters, which are such identified that the stationary conditions satisfy the governing equations. Findings - The derivation is simple, and the obtained variational principle is conciser than that obtained by Kalaawy, who introduced two special functions. Originality/value - This paper suggests an effective approach to the inverse problem of the calculus of variations.