Temporal evolution of the irrotational and solenoidal cavity modes

An outline of the evolutionary approach to time-domain electromagnetics is presented in a compact form available for practical using. A cavity is loaded with a given source of transient signal. The cavity field is presented via expansions in terms of the solenoidal and irrotational modes having time-dependent modal amplitudes. The differential equations with time derivative are derived from Maxwell´s equations for the amplitudes jointly with appropriate initial conditions. The frequency-domain theory usually interprets the irrotational modes as some static fields. Graphical results illustrating the time dependence of the irrotational and solenoidal modes will be exhibited in the presentation.