%0 Conference Proceedings %T Modeling of a new electron-streamer acceleration mechanism %+ Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E) %A Ihaddadene, K. M. A. %A Dwyer, J. R. %A Liu, N. %A Celestin, Sebastien %< avec comité de lecture %B American Geophysical Union %C San Francisco, United States %V 2017 %8 2017 %D 2017 %Z 2017AGUFMAE32A..06I %K Atmospheric electricity %K ATMOSPHERIC PROCESSES %K Lightning %K Atmospheric %K NATURAL HAZARDS %Z Sciences of the Universe [physics]Conference papers %X Lightning stepped leaders and laboratory spark discharges in air are known to produce X-rays [e.g., Dwyer et al., Geophys. Res. lett., 32, L20809, 2005; Kochkin et al., J. Phys. D: Appl. Phys., 45, 425202, 2012]. However, the processes behind the production of these X-rays are still not very well understood. During discharges, encounters between streamers of different polarities are very common. For example, during the formation of a new leader step, the negative streamer zone around the tip of a negative leader and the positive streamers initiated from the posiive part of a bidirectional space leader strongly interact. In laboratory experiments, when streamers are approaching a sharp electrode, streamers with the opposite polarity are initiated from the electrode and collide with the former streamers. Recently, the encounter between negative and positive streamers has been proposed as a plausible mechanism for the production of X-rays by spark discharges [Cooray et la., JASTP, 71, 1890, 2009; Kochkin et al., J. Phys. D: Appl. Phys., 45, 425202, 2012], but modeling results have shown later that the increase of the electric field involved in this process, which is above the conventional breakdown threshold field, is accompanied by a strong increase of the electron density. The resulting increase in the conductivity, in turn, causes this electric field to collapse over a few tens of picoseconds, preventing the electrons reaching high energies and producing significant X-ray emissions [e.g., Ihaddadene and Celestin, Geophys. Res. Lett., 45, 5644, 2015]. In this work, we will present simulation results of a new electron acceleration mechanism for producing runaway electron energies above hundred keV. The mechanism couples multiple single streamers and streamer head-on collisions, similar to a laboratory discharge, and is suitable for explaining the high-energy X-rays produced by discharges in air and by lightning stepped leaders. %G English %L insu-03570121 %U https://insu.hal.science/insu-03570121 %~ OBSPM %~ INSU %~ CNRS %~ UNIV-ORLEANS %~ CNES %~ OSUC %~ LPC2E %~ PSL %~ OBSPM-PSL %~ TEST3-HALCNRS