![]() ![]() The remaining 10 % occur as so-called cloud-to-ground flashes. This type of lightning accounts for about 90 % of the total lightning discharges. The former occur between clouds or within a cloud and have no contact with the ground. There are both cloud-to-cloud discharges and cloud-to-ground discharges. This process is then perceived as thunder. When this upward streamer connects with the downward leader, we generally speak of a “flash” or a lightning discharge.Īt the moment of discharge, the leader heats up strongly, causing the air around it to expand. In case a so-called “stepped-leader” starts growing and developing branches out to different degrees, a so-called upward "streamer" is emitted from objects on the ground. This first-stroke leader develops stepwise towards a charge region of the opposite polarity (negative or positive) in the cloud, an object or directly to ground. To equalise two differently charged regions in a thundercloud, between thunderclouds or between a thundercloud and the ground, an electrically conductive channel called "leader" is formed. The necessary process of charge separation during the formation or growth of a thundercloud has not yet been fully explained. Lightning discharges occur in electrically charged thunderclouds as compensation for differently charged regions. For Lukas Schwalt and project manager Stephan Pack, the field of research ranges from the physical principles of lightning discharge processes and the analysis of the effects of lightning discharges on high-voltage systems to lightning protection issues of structures and living beings. In the last 15 years, several core areas have developed at TU Graz where basic research is being carried out to investigate the natural phenomenon of "lightning discharges". ![]()
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