This is the first paragraph of an article in the June 9th issue of Nature,
pages 799-801 -- the authors have demonstrated that lightning intensifies
the sporadic-E layer. Full article is available at your library.

Lightning-induced intensification of the ionospheric sporadic E layer
C. J. Davis1 and C. G. Johnson1

Top of pageA connection between thunderstorms and the ionosphere has been
hypothesized since the mid-1920s1. Several mechanisms have been proposed to
explain this connection2, 3, 4, 5, 6, 7, and evidence from modelling8 as
well as various types of measurements9, 10, 11, 12, 13, 14 demonstrate that
lightning can interact with the lower ionosphere. It has been proposed, on
the basis of a few observed events15, that the ionospheric 'sporadic E'
layer-transient, localized patches of relatively high electron density in
the mid-ionosphere E layer, which significantly affect radio-wave
propagation-can be modulated by thunderstorms, but a more formal statistical
analysis is still needed. Here we identify a statistically significant
intensification and descent in altitude of the mid-latitude sporadic E layer
directly above thunderstorms. Because no ionospheric response to
low-pressure systems without lightning is detected, we conclude that this
localized intensification of the sporadic E layer can be attributed to
lightning. We suggest that the co-location of lightning and ionospheric
enhancement can be explained by either vertically propagating gravity waves
that transfer energy from the site of lightning into the ionosphere, or
vertical electrical discharge, or by a combination of these two mechanisms.