%0 Journal Article
%T Ground to Cloud Lightning Flash Currents and Electric Fields: Interaction with Aircraft and Production of Ionosphere Sprites
%A P. R. P. Hoole
%A S. Thirukumaran
%A Harikrishnan Ramiah
%A Jeevan Kanesan
%A S. R. H. Hoole
%J Journal of Computational Engineering
%D 2014
%R 10.1155/2014/869452
%X This paper presents for the first time a case for the importance of ground to cloud (upward leader) lightning flash parameters for safety testing of direct aircraft-lightning interaction and protection of wind turbines, as well as the importance of radiated electric fields for indirect lightning-aircraft interaction and generation of electric discharges called sprites and halos in the ionosphere. By using an electric circuit model of the transverse magnetic waves along the return stroke channel, electric currents at ground level as well as cloud level are determined for both the cloud to ground lightning flash and the ground to cloud lightning flash. We show that when an aircraft triggers lightning, the electric currents will be much more severe in current magnitude, rate of rise of currents, and frequency spectrum than otherwise and are more severe than the parameters observed for the usual and well monitored (and measured) cloud to ground (downward leader) flashes. The rate of rise of currents and the frequency spectrum of the ground to cloud lightning flash are also given here. The electric fields radiated by the lightning flashes that would appear in the ionosphere are presented for both the earth flash and the ground to cloud flash. 1. Lightning The majority of the lightning flashes encountered at ground are the negative, downward flashes where the lightning leader stroke emanates from the thundercloud and makes contact with the ground. Once the contact is made, the second, electrically severe return stroke¡ªsevere because it now has an ionized channel from the leader easing the flow of current¡ªis generated at the earth end and travels along the leader channel towards the cloud [1, 2]. These downward flash return stroke currents are measured at ground and used as standard current for testing both ground equipment and aircraft body. The other type of flash, less common, is the ground to cloud flash (upward leader and downward return stroke) which usually emanates from tall earthed structures, where the leader starts from the ground object and moves upward. Once the leader makes contact with the cloud, another downward stroke is initiated at the cloud, and by the time it reaches ground its current magnitude as well as rate of rise of currents is attenuated by the resistive components of the now ionized channel. It has been shown that the return stroke is a transverse magnetic wave [3], and it is modelled well by a travelling wave on a distributed (as opposed to lumped parameter) transmission line with resistance, inductance, and capacitance elements
%U http://www.hindawi.com/journals/jcengi/2014/869452/