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The Physics of Lightning Flash and Its Effects

COST Action P18 2005-2009 Chair: Rajeev Thottappillil, Sweden Vice-chair: Farhad Rachidi, Switzerland Web: www.costp18-lightning.org 19 COST countries and 4 non-COST countries. The Physics of Lightning Flash and Its Effects. Issues in lightning research.

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The Physics of Lightning Flash and Its Effects

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  1. COST Action P18 • 2005-2009 • Chair: Rajeev Thottappillil, Sweden • Vice-chair: Farhad Rachidi, Switzerland • Web: www.costp18-lightning.org • 19 COST countries and 4 non-COST countries The Physics of Lightning Flash and Its Effects

  2. Issues in lightning research 1)   Phenomenology of processes in the lightning flash? 2)   Lightning initiation in thunderclouds? 3)   Lightning stepped leader and dart leader? 4)   Lightning attachment to objects? 5)   Lightning return stroke? 6)  X-rays and gamma-rays emission associated with lightning? 7)  Ball lightning? 8)  Lightning initiation of transient luminous events, called sprites, elves, and blue jets, in the mesosphere and ionosphere? 9)  Production of the trace gas species in the atmosphere by the hot plasma channel and corona in lightning discharge? 10)Inferring properties of lightning processes from remote measurements of electromagnetic radiation from lightning? No single group has expertise in all these issues. 2005-12-12 Split Workshop Rajeev.Thottappillil@angstrom.uu.se

  3. Scientific Programme The main objective of the Action is to increase our knowledge of the physics of the lightning discharge and of its effects on natural and man-made systems. Examples of natural system – climate, atmospheric chemistry, global electric circuit Examples of man-made system – electrical and communication networks, railway network, flying objects, buildings and other facilities. This part has relevance to EMC and COST 286. However, it is the physical basis of the lightning interaction that is dealt with within COST P18. 2005-12-12 Split Workshop Rajeev.Thottappillil@angstrom.uu.se

  4. Scientific Programme Division of research tasks (Work Groups) WG1. Measurement of properties of varioustypes of lightning discharges WG2. Phenomenology and modelling of the processes in the lightning flash WG3. Physics and models for the lightning attachment to objects WG4. Inverse source problems in lightning WG5. Mesospheric transient luminous events associated with lightning 2005-12-12 Split Workshop Rajeev.Thottappillil@angstrom.uu.se

  5. WG1. Measurement of properties of various types of lightning discharges • Emphasis on time-correlated measurements on the same lightning using diverse instruments (currents, electromagnetic fields, optical measurements, x-rays, gamma-rays) • Time scale from nanoseconds to milliseconds • Establishment of a data bank on the lightning parameters, including a databank on the characteristics of the electromagnetic radiation of lightning from ELF to gamma rays (could be beneficial for COST 286). 2005-12-12 Split Workshop Rajeev.Thottappillil@angstrom.uu.se

  6. Measurements using Rocket-triggered lightning University of Florida, Gainesville, USA 2005-12-12 Split Workshop Rajeev.Thottappillil@angstrom.uu.se

  7. Measurements at Gaisberg tower, Austria (This tower is struck by lightning on average 65 times in a year) 2005-12-12 Split Workshop Rajeev.Thottappillil@angstrom.uu.se

  8. 2 3 4 7 8 5 9 1 6 M M M ICC Lightning return stroke Peak current: 2000 A – 300 000 A Average speed: 1-2x108 m/s Typical maximum current rate of rise 100 kA/s Channel radius: 1-2 cm Channel temperature: 30000 K Saturation level 2005-12-12 Split Workshop Rajeev.Thottappillil@angstrom.uu.se

  9. Lightning return stroke – conti. Why there are so large variations in the peak current, charge, and optically measured speed between return strokes? Why there is continuing current (100-200 A for >40 ms) after some return strokes? Why some negative CG lightning flashes are single stroke flashes while majority of them are multiple-stroke flashes (1-26 strokes)? Why for some strokes there is more than one termination on ground, separated by a few meters to a few kilometres? A model for return stroke that could explain all the major observed characteristics. How is the physics of negative return stroke different from positive return stroke? Why positive lightning produces the most energetic return strokes, in terms of the largest value of peak currents and largest value of effective charge lowered? 2005-12-12 Split Workshop Rajeev.Thottappillil@angstrom.uu.se

  10. WG2. Phenomenology and modelling of the processes in the lightning flash Detailed analysis of the measurements carried out in WG1 will fill the gaps in our present understanding of the phenomenology of the processes. Models for various lightning processes: lightning initiation, stepped leader, lightning attachment, return stroke, continuing current, M component, K changes, and dart leader. To understand the mechanism of the production of the trace gas species in the atmosphere by the hot plasma channel and corona in lightning discharge. To understand the connection between the particular characteristics of lightning flashes and the associated observation of luminous events in the mesosphere and the lower ionosphere. 2005-12-12 Split Workshop Rajeev.Thottappillil@angstrom.uu.se

  11. x-rays and gamma-rays emission associated with lightning • A new topic in lightning research. • Very few reliable measurements. • What processes in lightning give rise to these? What is the physics behind it? 2005-12-12 Split Workshop Rajeev.Thottappillil@angstrom.uu.se

  12. Production of the trace gas species in the atmosphere by the hot plasma channel and corona in lightning discharge At global scale, lightning as NOx source represent 10-30% of total. R1: O2 O + O R2: O + N2 NO + N R3: N + O2 NO + O R4: NO + O3 NO2 + O2 R5: NO2 + O  NO + O2 Net: O + O3  2O2 How the hot plasma channel of the lightning return stroke, and the corona produced during the pre-breakdown processes reacts with the molecules in air and produce trace gas species, most importantly NO and NOx? 2005-12-12 Split Workshop Rajeev.Thottappillil@angstrom.uu.se

  13. WG3. Physics and models for the lightning attachment to objects • Modelling the break-through phase (meeting between donward and upward leaders). • What determines the striking distance? How striking distance is related to the measurable parameters like charge and current? • Any difference in the attachment process when upward leaders are initiated from insulated objects (e.g., trees, rotor of windmills) as opposed to from grounded conducting objects (e.g., air terminals on top of buildings, towers)? • What are the conditions necessary for a tall object (e.g., tall tower, mountain top) to initiate long upward leader all the way to the cloud, even when there are no visible downward leader prior to that? • What is the physics of triggering of lightning by flying objects. • How the struck medium (e.g., tall towers) could influence the return stroke parameters? • What role surface arcs play in supplying the current (charge) involved in lightning return stroke? 2005-12-12 Split Workshop Rajeev.Thottappillil@angstrom.uu.se

  14. Lightning attachment to aircraft Models for lightning initiation by flying objects and attachment to flying objects. Bi-directional leader development 2005-12-12 Split Workshop Rajeev.Thottappillil@angstrom.uu.se

  15. Lightning attachment to objects– termination on earth Lightning current dissipation in soil. Surface arcing. Fulgurites production. First photograph of surface arcing (Triggered lightning, Sandia national lab., 1991) Evidence of surface arcing 2005-12-12 Split Workshop Rajeev.Thottappillil@angstrom.uu.se

  16. WG4. Inverse source problems in lightning • What can we learn about lightning from its electromagnetic radiation (radio frequency, microwave, infrared, visible light, ultraviolet, x-ray and gamma ray regions of spectrum). • Studying lightning discharge development inside clouds using interferometric and time-of-arrival of pulse techniques. • Models for radio wave propagation over different kinds of terrain, to compensate for propagation effects. 2005-12-12 Split Workshop Rajeev.Thottappillil@angstrom.uu.se

  17. Inferring properties of lightning processes from remote measurements of electromagnetic radiation from lightning • What can we learn about the physics of the processes in lightning by analysing its electromagnetic radiation (radio-frequency, visible light, x-rays, gamma rays)? • Mapping the 3-dimensional evolution of lightning channels within clouds by tracing the sources of radio-frequencies using time-of-arrival and interferometric techniques. 2005-12-12 Split Workshop Rajeev.Thottappillil@angstrom.uu.se

  18. WG5: Mesospheric transient luminous events associated with lightning Lightning initiation of transient luminous events, called sprites, elves, and blue jets, in the mesosphere and ionosphere A new topic. First observation in 1990. What role lightning play in the initiation of transient luminous event? Often sprites are associated with large positive return strokes and blue jets with large negative return strokes. How this coupling works? 2005-12-12 Split Workshop Rajeev.Thottappillil@angstrom.uu.se

  19. Dissemination plan - audience Target audience: Researchers working with different aspects of the physics of lightning Other interested audience: International standard making bodies concerned with lightning protection National and regional policy makers and planners concerned with weather and environmental issues related to lightning Insurance industry and service providers concerned with risk of damages and accidents due to lightning Manufacturing and service industry concerned with effective lightning protection 2005-12-12 Split Workshop Rajeev.Thottappillil@angstrom.uu.se

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