Diurnal variations of atmospheric potential gradient disruption near to high voltage power lines

The Earth's background potential gradient (PG) has a diurnal cycle (the 'Carnegie curve') that can be exhibited in fair weather when there are no local sources of space charge. High voltage power lines can create corona ions which are released into the atmosphere and can disrupt the natural PG. A fixed site monitoring station measured the vertical potential gradient at 1 s intervals alongside local weather conditions to investigate the time of day at which corona production is greatest downwind of a power line. In upwind conditions, the average PG curve returned correlates well with the Carnegie curve, but this is masked under downwind conditions. Overnight, the PG downwind of the monitoring station is more variable and more negative than upwind. Downwind of the power line there is significantly more variability of potential gradient after sunrise and before sunset on most days. (C) 2012 Elsevier Ltd. All rights reserved.