A series of perturbation experiments (Waterhole I, II, and III), in which ''holes'' were created in the F region ionosphere by explosive releases of large quantities of water vapor, has been conducted to test theories of the electrodynamic structure of auroral arcs. The water vapor releases created large (≈50-km diameter) holes in the ionosphere in and near structured premidnight auroral arcs. It was anticipated that these holes would interrupt or perturb the ionospheric current systems associated with the arcs and that this perturbation would in turn affect the acceleration mechanism responsible for the aurora. Results from the two successful rocket flights (Waterhole I and III) are presented, and it is shown that significant modifications of the energetic electron precipitation patterns were induced by both releases. The first release was made 10 km poleward of a discrete early evening auroral arc, and the perturbation caused a cessation of electron precipitation through the hole and a significant modification of the arc. The second release, which occurred on magnetic field lines connected to the center of a series of arcs, produced a much smaller hole mainly due to the preexisting low electron density and also induced a less striking energetic electron response. In this case the flux was enhanced. Various models and theories of the perturbation mechanism are discussed, and it is shown that both responses are consistent with current theories of the electrodynamic structure of auroral arcs.