HR: 1340h
AN: AE23A-0832    [Abstracts]
TI: Modelisation of electromagnetic radiation of negative stepped leader
AU: * L Helgoualc h, I
EM: helgoual@onera.fr
AF: Onera, 29 avenue de la Division Leclerc, Chatillon, 92322 France
AU: Lalande, P
EM: philippe.lalande@onera.fr
AF: Onera, 29 avenue de la Division Leclerc, Chatillon, 92322 France
AU: Vallee, J
EM: jerome.vallee@onera.fr
AF: Onera, 29 avenue de la Division Leclerc, Chatillon, 92322 France
AB: Experiments in laboratory and in stormy environments have shown that one of the main component of electromagnetic radiation of lightning is mainly due to the negative stepped leader in the VHF-UHF frequency band; the power radiated by the positive one is 1000 times lower than that by the negative one. This difference of radiation is due to the stepped propagation of the negative leader with which strong and fast pulses of current are associated. Just before the step, the negative discharge is composed of four zones: a resistive and conductive canal called negative leader, a high resistive zone called positive streamers zone, a resistive and conductive canal called space leader, and an active head associated with a negative corona development. The strong current pulse occurs during the connection of the negative and space leaders. The time evolution of the current along the negative discharge is performed using a transmission line model in which the distributed capacitances and inductances remain constant while the distributed resistances vary as a function of currents. A current pulse injected at the extremity of the transmission line simulates the negative corona development. The radiated field is computed from the current distribution by integrating along the discharge the electromagnetic field radiated by elementary Hertz dipoles. From this model, the power radiated by the negative leader versus the altitude is investigated.
DE: 3324 Lightning
SC: Atmospheric and Space Electricity [AE]
MN: 2004 AGU Fall Meeting