Some Analyses of Atmospheric Electric-Field Gradients

The earth maintains surprisingly large voltage gradients, Ez [V/m], between its surface and a conductive ionosphere above 100 km, with fair-weather measurements averaging about 160 V/m near the surface, positive upwards. These gradients are easily detected but difficult to quantify with accuracies better than a few percent. Data records survive from several sites dating to the early 1900's. Measured Ez are noisy, with extreme values during brief intervals [0.1 sec] exceeding ±1,000 V/m. With yearly data at longer sampling intervals [30 min], extreme values typically range between –100 and +500 V/m, with unfiltered averages and standard deviations near 180 ± 75 V/m. [Figure 1].