High-speed video of lightning and x-ray pulses during the 2009–2010 observation campaigns in northeastern Spain

This paper summarizes results obtained by the 2009–2010 field campaigns conducted in northeastern Spain using a high speed camera, VHF interferometer, VLF lightning location system and scintillation detectors for energetic radiation. The main purpose was to obtain new insight into the lightning processes which emit x/γ radiation. For just one (very close) lightning strike, 99 x-ray pulses were emitted within 0.86 ms and had an energy higher that 10 keV. This burst was associated with the final stages of a downward negative leader. The high-speed camera data also allowed to identify various previously unreported features in different types of cloud-to-ground lightning flashes. At video frame rates of 10,000 fps, some branches of negative leaders of cloud-to-ground flashes were illuminated for the duration of only one frame. During positive cloud-to-ground flashes, the high speed videos showed an intense activity of recoil leaders. In the case of intra-cloud lightning, the VHF interferometer network did not present a clear relation between detections and visible leader. Instead, bursts of VHF detections corresponded visually to a long-lasting bright channel under the cloud base.