Cj. Rodger et al., Lower ionospheric modification by lightning-EMP: Simulation of the night ionosphere over the United States, GEOPHYS R L, 28(2), 2001, pp. 199-202
It has recently been suggested that successive intense lightning-electromag
netic pulse (EMP) events could cause significant large-scale changes to the
properties of the nighttime lower ionosphere. In order to examine this qua
ntitatively, data on lightning detected over the United States are combined
with the output from a simulation code. During the course of a night stron
g lightning-EMP events can lead to significant (similar to 100% or even gre
ater) increases in the electron density of the lower ionosphere, with the l
argest increases at similar to 90 km altitude. Regions with significant dec
reases in electron density are also possible. It is shown that changes in t
he electron temperature of the lower ionosphere are unlikely to be signific
ant. The time required to produce large-scale changes of ionospheric electr
on density above an active thunderstorm may explain the observation of a th
understorm "modification time" before red sprite activity is initiated.