The total ponderomotive force and inhomogeneity indicators

Droplets on outdoor high-voltage equipment suffer a total ponderomotive force which is non-vanishing in general. We show that this force can be given as a series of inhomogeneity indicators of the undisturbed electric field in the absence of the droplet. We use 2d and 3d Fourier techniques to prove the series expansion as a relation between the solutions of two Poissonʹs equations on different domains. The order of magnitude of the terms in the series expansion is discussed. It is found that the expansion converges fast in applicatory cases. The results are applied for droplets on a realistically shaped insulator.