Relativistic electron beams above thunderclouds
Non-luminous relativistic electron beams above thunderclouds have been detected by the radio signals of low frequency 40400 kHz which they radiate. The electron beams occur 29 ms after positive cloud-to-ground lightning discharges at heights between 2272 km above thunderclouds. Intense positive lightning discharges can also cause sprites which occur either above or prior to the electron beam. One electron beam was detected without any luminous sprite which suggests that electron beams may also occur independently of sprites. Numerical simulations show that beams of 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 impulsive current 3 103 Am2 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.