• Dr. Nelson Theethayi (past member, presently with Bombardier, Västerås)
Collaborators: Austrian Electrotechnical Association, Vienna, Austria (Dr. Gerhard Diendorfer); University of Florida, Gainesville, USA (Prof. Vlad Rakov, Prof. Martin Uman); Swiss Federal Institute of Technology, Lausanne (EPFL), Switzerland (Prof. Farhad Rachidi); Ecole d'ingénierie et de Gestion du Canton de Vaud (HEIG-Vd), Yverdon, Switzerland (Prof. Marcos Rubinstein); Federal Armed Forces Research University, Munich, Germany (Prof. Fridolin Heidler).
The research in lightning is as old as the research in electricity. In 1750 Benjamin Franklin suggested an experiment that later proved lightning is an electrical discharge. Two years later the experiment was first successfully performed in France, followed by in England and Belgium. The Franklin rod for protecting buildings from the effects of lightning strike was one of the first electrical devices. From the very beginning lightning research was interdisciplinary, attracting scientists from different branches of science. It was C.T.R. Wilson, recipient of the Nobel Prize for Physics in 1927 for the invention of the cloud chamber, who first determined the amount of electrical charges involved in lightning and thunderstorms by remote electric field measurement.
Lightning is a transient electric discharge, which lasts, on average, half a second and exhibits a path-length of some kilometers. The most common source of lightning on earth is the cumulonimbus cloud. A cloud-to-ground lightning can cause damage to an object on earth by directly attaching to it or by induced effects while striking somewhere near to the object. Airborne vehicles passing through electrified clouds can trigger lightning. Researchers around the world have performed experiments to determine the properties of lightning using photography, spectroscopy, electromagnetic field measurements, and direct measurements of currents when lightning strikes tall objects. However, knowledge of the phenomenology of processes in the lightning flash is not complete.
Research on lightning within the group includes analysis of measured electric field, magnetic fields, and optical records from lightning and directly measured currents and charges in lightning strikes to towers. The objective of the analysis and modeling is to derive new knowledge on the physics and effects of lightning. Besides, the group is active in the EU project COST P18: The Physics of Lightning Flash and its Effects: www.costp18-lightning.org
Electromagnetic, field coupling, Maxwell's equations, transmission line model, return stroke.
D. Flache, V. A. Rakov, F. Heidler, W. Zischank, and R. Thottappillil, Initial-stage pulses in upward lightning: Leader/return stroke versus M-component mode of charge transfer to ground, Geophysical Research Letters, Vol. 35, L13812, doi:10.1029/2008GL034148, 2008.
Thottappillil, R., V. A. Rakov, and N. Theethayi, Expressions for far electric fields produced at an arbitrary altitude by lightning return strokes, J. Geophys. Res., 112, D16102, doi:101029/2007JD008559.
Nelson Theethayi and Rajeev Thottappillil, Some Issues Concerning Lightning Strikes to Communication towers, Journal of Electrostatics, Vol. 65, Issues 10-11, October 2007, pp. 689-703.
Thottappillil, R., and V. A. Rakov, Comment on “Radio frequency radiation beam pattern of lightning return strokes: A revisit to theoretical analysis” by Xuan-Min Shao, Abram R. Jacobson, and T. Joseph Fitzgerald, J. Geophys. Res., 110, D24105, doi:10.1029/2004JD005729, 2005.
Megumu Miki, Vladimir Rakov, Takatoshi Shindo, Diendorfer Gerhard, Martin Mair, Fridolin Heidler, Wolfgang Zischank, M.A. Uman, Rajeev Thottappillil, Daohong Wang, Initial Stage in Lightning Initiated from Tall Objects and in Rocket-Triggered Lightning, J. Geophysical Research, 110, D02109, 2005.
Thottappillil, R., M.A. Uman, N. Theethayi, Electric and magnetic fields from a semi-infinite antenna above a conducting plane, J. Electrostatics, 61, 209-221, 2004.
Rakov, V.A., R. Thottappillil, J. Schoene, Comments on 'On the concepts used in return stroke models applied in engineering practice', IEEE Transactions on Electromagnetic Compatibility, Vol. 45, p. 567, Aug. 2003.
Miki, M., T. Shindo, V.A. Rakov, M.A. Uman, K.J. Rambo, G.H. Schnetzer, G. Diendorfer, M. Mair, F. Heidler, W. Zischank, R. Thottappillil, D. Wang, Die Anfangphase von Aufwärtsblitzen, ETZ, Heft 3-4, 50-55, 2003.
Thottappillil, R., M.A. Uman, Reply to the ‘Comment on “Return stroke transmission line model for stroke speed near and equal that of light by R. Thottappillil, J. Schoene, and M.A. Uman’ ” by G. Kordi, R. Moini, and V.A. Rakov, Geophysical Research Letters, 29, May 2002.
Thottappillil, R., Electromagnetic Pulse Environment of Cloud-to-Ground Lightning for EMC studies, IEEE Trans. On Electromagnetic Compatibility, 44, 203-213, 2002.
Thottappillil, R., and V.A. Rakov, On different approaches to calculating lightning electric fields, Journal of Geophysical Research, 106, 14191-14205, 2001.
Thottappillil, R., J. Schoene, and M.A. Uman, Return stroke transmission line model for stroke speed near and equal that of light, Geophysical Research Letters, 28, 3593-3596, 2001.
Rakov V.A., D.E. Crawford, K.J. Rambo, G.H. Schnetzer, and R. Thottappillil, M-component mode charge transfer to ground in lightning discharges, Journal of Geophysical Research, 106, 22817-22831, 2001.
Popov, M., S. He, R. Thottappillil, Reconstruction of lightning currents and return stroke model parameters using remote electromagnetic fields, Journal of Geophysical Research, 105, 24469-24481, 2000.
Silfverskiöld, S, R. Thottappillil, Y. Ming, V. Cooray, and V. Scuka, Induced voltages in a low voltage power installation network due to lightning electromagnetic fields: an experimental study, IEEE Transactions on Electromagnetic Compatibility, 41, 265-271, 1999.
Thottappillil, R., M. A. Uman, and V. A. Rakov, Treatment of retardation effects in calculating the radiated electromagnetic fields from the lightning discharge, J. Geophys. Res., 103, 9003-9013, 1998.
V. A. Rakov, M. A. Uman, K. J. Rambo, M. I. Fernandez, R. J. Fischer, G. H. Schnetzer, R. Thottappillil, A. Eybert-Berard, J. P. Berlandis, P. Lalande, A. Bonamy, P. Laroche, and A. Bondiou-Clergerie, New insights into lightning processes gained from triggered-lightning experiments in Florida and Alabama, J. Geophys. Res., 103, 14117-14130, 1998.
Thottappillil, R., V. A. Rakov, and M. A. Uman, Distribution of charge along the lightning channel: Relation to remote electric and magnetic fields and to return-stroke models, J. Geophys. Res., 102, 6987-7006, 1997.