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X-ray bursts associated with leader steps in cloud-to-ground lightning
Dwyer, J. R.; Rassoul, H.
K.; Al-Dayeh, M.; Caraway, L.; Chrest, A.; Wright, B.; Kozak, E.;
Jerauld, J.; Uman, M. A.; Rakov, V. A.; Jordan, D. M.; Rambo, K. J.
Geophysical Research Letters (2004), Volume Date 2005, 32(1),
CODEN: GPRLAJ; ISSN: 0094-8276. English.
X-ray and elec. field
measurements were made during 5 nearby neg. natural lightning strikes
in north central Florida during the summer of 2004. The observed x-ray
emission typically was detected ~1 ms before the 1st return stroke,
during the stepped-leader phase, and had energies extending up to a few
hundred keV. The X rays were produced in discrete, intense bursts
emitted in coincidence with the formation of the leader steps,
demonstrating unambiguously that the source of lightning X rays is
closely related to the stepping process. The x-ray emission from
lightning stepped leaders is found to be remarkably similar to that
from lightning dart leaders, suggesting that these different types of
leaders share a common mechanism. The reported observations have
important implications for understanding how runaway breakdown occurs
and how lightning leaders propagate.