Estimation of Ionospheric Reflection Heights Using CG and IC Lightning Electric Field Waveforms

Ionospheric reflection heights for VLF/LF electromagnetic waves were estimated using electric field waveforms of negative cloud-to-ground return strokes (-CGs) and compact intracloud discharges (CIDs) that occurred in the same thunderstorm over the Gulf of Mexico. We analyzed 42 CC and 42 CID waveforms that were observed at night between 2 and 4 a.m. (Local Time) on August 7, 2016. All the lightning events occurred at distances ranging from 143 to 216 km. We compared three different methods to estimate ionospheric reflection heights. The first and second methods are based on using CGs, whose field waveforms are radiated from channel sections near the ground surface, and differ in using either planar or spherical earth geometry. The third method is based on using elevated sources (CIDs) and planar geometry. For CGs, different measures of skywave delay relative to the ground wave were considered. Differences between the mean ionospheric reflection heights computed using all the different methods were found to he less than 3%.