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This report characterizes long-term fluctuations in static electric field and ion concentrations near alternating-current transmission lines. Measurements of these parameters and meteorological data were collected at two sites in New Hampshire over more than two years. The dependence of field and ion levels on wind indicated that corona activity produced localized downwind enhancement of ambient atmospheric levels. Increases were observed for the positive field at all monitoring stations and at one station for negative fields. Enhanced downwind positive ion concentrations were prevalent at all stations. Increases in downwind negative ion concentrations were also present for all stations, but were much less frequent. The magnitudes of the enhanced fields and ion concentrations exceeded the range of upwind (ambient) values only for a small percentage of the time under most conditions. These results indicate the difficulty in using short-term survey measurements near transmission lines to characterize long-term perturbations to ambient atmospheric electric field and ion concentrations by corona-generated space charge.