Geophysical Research Letters
X-ray and electric field measurements were made during five nearby negative natural lightning strikes in north central Florida during the summer of 2004. The observed X-ray emission typically was detected ∼1 ms before the first 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.
Dwyer, Joseph R.; Rassoul, Hamid K.; al-Dayeh, M.; Caraway, Lee; Chrest, A.; Wright, Brian F.; and Kozak, E., "X-ray Bursts Associated With Leader Steps In Cloud-To-Ground Lightning" (2005). Aerospace, Physics, and Space Science Faculty Publications. 506.