A New Approximate Method for Lightning-Radiated ELF/VLF Ground Wave Propagation over Intermediate Ranges

Figure 3

Comparison of the vertical electric field calculated by our approximate formula in (6) and Wait’s original formula in (3) for the ocean propagation path considering the earth curvature at different distances of (a) 200 km, (b) 500 km, (c) 1000 km, and (d) 1500 km. Wait’s original formula is solved by the Newton–Raphson root-finding method. The polarity of a vertical electric field pointing downward is defined to be positive.

(a)

(b)

(c)

(d)