An improved Darwin approximation in the classical electromagnetism

Abstract

Darwin approximation, a non-relativistic submodel of the Maxwell's equations, has been used for theoretical and computational investigations of magnetized plasmas. In this short paper, an improved Darwin approximation is proposed, which is applicable not only to the Coulomb gauge but also to the Lorenz counterpart. The proposed approximation exactly satisfies the conservation of charge, momentum, and energy under the use of the Lorenz and Coulomb gauges.