Relativistic electron beams above thunderclouds
Olivier Chanrion2011, Atmospheric Chemistry and Physics
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Abstract
Non-luminous relativistic electron beams above thunderclouds are detected by radio remote sensing with low frequency radio signals from ∼40-400 kHz. The electron beams occur ∼2-9 ms after positive cloud-to-ground lightning discharges at heights between ∼22-72 km above thunderclouds. The positive lightning discharges also cause 5 sprites which occur either above or before the electron beam. One electron beam was detected without any luminous sprite occurrence which suggests that electron beams may also occur independently. Numerical simulations show that the beamed electrons partially discharge the lightning electric field above thunderclouds and thereby gain a mean energy of ∼7 MeV to transport a total charge of ∼10 mC upwards. The impul-10 sive current associated with relativistic electron beams above thunderclouds is directed downwards and needs to be considered as a novel element of the global atmospheric electric circuit. ulation of energetic seed particles to initiate an electromagnetically radiating non-linear 15553 ACPD Abstract Relativistic electron beams M. Füllekrug et al. Title Page Abstract Relativistic electron beams M. Füllekrug et al. Title Page Abstract Relativistic electron beams M. Füllekrug et al. Title Page Abstract Relativistic electron beams M. Füllekrug et al.
Key takeaways
- Two much smaller consecutive bursts of electromagnetic radiation occur ∼4.4 ms and ∼8.9 ms after the lightning discharge and do not deposit a large fraction of their electromagnetic energy in the frequency range from ∼5-16 kHz which is untypical for conventional lightning discharges.
- Numerical simulations of relativistic electron beams above thunderclouds predict theoretically broadband bursts of electromagnetic radiation with a flat spectrum following sprite producing lightning discharges (Füllekrug et al., 2010) in agreement with our experimental observations.
- Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | sensitivity analysis was performed to determine the optimum distance between the lightning discharge and the radio receiver which maximizes the signals of the ground and sky wave.
- The electron beams are located above the thundercloud and below the main body of sprites or the electron beams shortly follow the sprite luminosity.
- The electromagnetic radiation bursts from the lightning discharge and the consecutive electron beam exhibit time delays from ∼2-9 ms.
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