X-ray emissions produced by stepping lightning leaders

Summary form only given. X-ray bursts have been observed in association with rocket-triggered lightning and natural cloud-to-ground lightning [e.g., Dwyer et al., Science, 299, 694-697, 2003; Saleh et al., JGR, 114, D17210, 2009; Schaal et al., JGR, 117, D15201, 2012]. Moreover, recent measurements at the International Center for Lightning Research and Testing (ICLRT) [e.g., Dwyer et al., GRL, 32, L01803, 2005; Howard et al., GRL, 35, L13817, 2008] have established a correlation between these X-ray measurements and the stepping process of lightning leaders. Additionally, it has been suggested that the Relativistic Runaway Electron Avalanche (RREA) mechanism is not likely to be responsible for this phenomenon [Dwyer et al., GRL, 31, L12102, 2004]. These X-rays may instead originate from the acceleration of runaway electrons in the lightning leader field during negative corona flash processes [Celestin and Pasko, JGR, 116, A03315, 2011]. However, the properties of X-ray bursts from lightning are poorly known, mainly due to the low fluence of photons detected from the ground.