Download or read book Low Pressure Electrical Discharge Experiment to Simulate High Altitude Lightning Above Thunderclouds written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-05 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recently, extremely interesting high-altitude cloud-ionosphere electrical discharges, like lightning above thunderstorms, have been observed from NASA's space shuttle missions and during airborne and ground-based experiments. To understand these discharges, a new experiment was conceived to simulate a thundercloud in a vacuum chamber using a dielectric in particulate form into which electrodes were inserted to create charge centers analogous to those in an electrified cloud. To represent the ionosphere, a conducting medium (metallic plate) was introduced at the top of the chamber. It was found that for different pressures between approximately 1 and 300 mb, corresponding to various upper atmospheric altitudes, different discharges occurred above the simulated thundercloud, and these bore a remarkable similarity to the observed atmospheric phenomena. At pressures greater than 300 mb, these discharges were rare and only discharges within the simulated thundercloud were observed. Use of a particulate dielectric was critical for the successful simulation of the high-altitude lightning. Jarzembski, M. A. and Srivastava, V. Marshall Space Flight Center ...

Download or read book Low pressure Electrical Discharge Experiment to Simulate High altitude Lightning Above Thunderclouds written by M. A. Jarzembski and published by . This book was released on 1995 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Lightning Initiation Due to Hydrometeor Collisions in Thunderclouds written by Qiheng Cai and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In order to initiate streamers and leaders under thunderstorm conditions, the electric field should reach values higher than the critical breakdown field. However, the maximum electric field in thunderstorms measured by balloons is much smaller than the breakdown field. In order to investigate the electric field amplification required for streamer initiation in thunderclouds, in this dissertation work, we introduce two numerical models of two hydrometeors in uniform electric fields.The first model is two separated spherical hydrometeors. We have found the relationship between minimum electric field required for streamer initiation and the particle radius. The larger the radius, the lower electric field required. Furthermore, we consider the model of two particles with different radii for streamer initiation including the process of photoionization feedback, which could initially produce photons and then trigger a secondary electron avalanche to reduce the threshold electric field required for streamer initiation. The relationship between radii of particles for successful streamer initiation in the gap is investigated. We also demonstrate that for realistic particle dimensions, the avalanche to streamer transition is possible in a local electric field just slightly above the minimum field required for propagation of positive streamers in air.Considering that the connection of two spheres would lead to increase of the electric field at the outer periphery, and outside space represents a larger volume available for the photoionization feedback in comparison with the relatively small gap between two spheres, the second model of two spherical particles connected with a discharge channel is investigated. We also investigate the relationship of the radii of these two particles for streamer initiation on the outside periphery. Furthermore, we estimated the frequency of streamer initiation using three realistic hydrometeor size model distributions available in the literature and found that the scenario of streamer initiation on the outside periphery is only possible for relatively high electric fields, which are close to half of the breakdown electric field, at typical thundercloud altitudes of 3 and 6 km.

Download or read book Numerical Modeling of Leader Discharge Mechanisms in Lightning Blue Jets Gigantic Jets and Sprites written by Caitano Da Silva and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The work presented in this dissertation is dedicated to the investigation of leader discharge mechanisms in lightning and transient luminous events. We introduce two new numerical models of the leader process that capture its onset and propagation, as briefly described below.The first theoretical model simulates air heating and streamer-to-leader transition in gas discharges. The model accounts for all physical processes known to play a role in the conversion of a streamer corona to a leader channel. Detailed discussion on the role of electron detachment in the development of the thermal-ionizational instability that triggers the spark development in short air gaps is presented. The dynamics of fast heating by quenching of excited electronic states is discussed and the scaling of its main channels with ambient air density is quantified. The developed model is employed to study the streamer-to-leader transition process and to obtain its scaling with ambient air density. The introduced methodology for estimation of leader speeds is based on the assumption that the propagation of a leader is limited by the air heating of every newly-formed leader section. It is demonstrated that the streamer-to-leader transition time has an inverse-squared dependence on the ambient air density at near-ground pressures, in agreement with similarity laws for Joule heating in a streamer channel. Model results indicate that a deviation from this similarity scaling occurs at very-low air densities, where the rate of electronic power deposition is balanced by the channel expansion, and air heating from quenching of excited electronic states is very inefficient. These findings place a limit on the maximum altitude at which a hot and highly-conducting lightning leader channel can be formed in the Earth's atmosphere. This result is important for understating of the gigantic jet discharges between thundercloud tops and the lower ionosphere. Our simulations of leader propagation at stratospheric altitudes demonstrate that initial speeds of gigantic jets are consistent with the leader propagation mechanism, and that the observed acceleration in gigantic jets can be attributed to the expansion of its streamer zone in a medium of exponentially-decreasing air density. This process defines the existence of an altitude at which the streamer zone becomes so long that it dynamically extends all the way to the ionosphere. We extend the air heating model to simulate the effects of strong currents flowing in sprites in the mesosphere. We show that fast air heating (due to quenching of excited electronic states) in sprite cores can produce >0.01 Pa pressure perturbations on the ground, observed in association with sprites. The second theoretical model simulates the electromagnetic radiation generated during the initial breakdown stage of lightning discharges. We use this model to describe in detail how the leader discharge dynamics generates the so-called initial breakdown pulses (IBPs) and narrow bipolar events (NBEs) observed with multi-station electric field change sensors on the ground. IBPs have been correlated with individual bursts of light that appear to be illuminations of a lightning leader channel; as a flash evolves the location of IBP sources inside the cloud coincides with the position of negative leaders as determined by a VHF lightning mapping system. NBEs are electric field signatures with broadband waveforms resembling classic IBPs in both amplitude and duration. Nonetheless, NBEs are quite peculiar in the sense that very infrequently they are followed by conventional lightning processes. Only a small fraction of positive-polarity NBEs happen as the first event in an otherwise regular intracloud lightning discharge. Typically, the initiator-type of NBEs has no difference with other NBEs that did not start lightning, except for the fact that they occur deeper inside the thunderstorm (i.e., at lower altitudes). In this dissertation we propose that IBPs and NBEs are the electromagnetic transients associated with the sudden (i.e., stepwise) elongation of the initial negative leader extremity in the thunderstorm electric field. To demonstrate our hypothesis we use a novel model of the leader electrodynamics. It consists of a generalization of electrostatic and transmission-line approximations existing in the refereed literature. We demonstrate how the IBP and NBE waveform characteristics directly reflect the properties of the bidirectional lightning leader (such as step length, for example) and amplitude of the thunderstorm electric field.

Download or read book Initiation of Streamers from Thundercloud Hydrometeors and Implications to Lightning Initiation written by Samaneh Sadighi and published by . This book was released on 2015 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt: Electric field values measured inside thunderclouds have consistently been reported to be up to an order of magnitude lower than the value required for the conventional electrical breakdown of air. This result has made it difficult to explain how lightning frequently occurs in thunderclouds. A few different theories have been offered to explain the lightning initiation process, one of them being the theory of lightning initiation from hydrometeors. According to this theory, lightning can be initiated from electrical discharges originating around thundercloud water or ice particles in the measured thundercloud electric field. These particles, called hydrometeors, can cause significant enhancement of the thundercloud electric field in their vicinity, increasing the probability to initiate streamers that are precursor discharges for the hot lightning leader channel. The first step in improving our understanding of lightning initiation is to study streamers. For this dissertation research, we have focused our efforts on studying streamer initiation and propagation from thundercloud hydrometeors. For the first part of this study, we have further investigated the idea proposed by Liu et al. [2012b] to study streamers from ionization column hydrometeors in thundercloud conditions. We have performed simulations for ambient electric field values of 0.5E[k] at thundercloud altitudes, and obtained successful streamer formation, confirming the work of Liu et al. [2012bJ. Reducing the ambient electric field to as low as 0.3E[k] affects the streamer's ability to propagate stably. According to our results, initiation of stable streamers from thundercloud hydrometeors in a 0.3E[k] electric field is possible, only if enhanced ambient ionization levels (e.g., the ionization created by corona discharges around the same or other nearby hydrometeors) are present ahead of the streamer. The magnitude and distribution of this ambient density may be a determining factor on whether the streamer forms, or branches during initiation. The branching of the streamer interrupts the stable streamer propagation and changes the dynamics of the streamer. We investigate the streamer branching behavior and characteristics, and test a theory that has recently been proposed to explain this phenomenon [Savel'eva et al., 2013]. We find that the geometry of the streamer head plays an important role in the streamer branching phenomena. The fast radial movement of the maximum streamer head curvature, combined with the slow reduction of the maximum curvature value, eventually leads the streamer head to branching. In order to verify whether an ionization column is a proper representation of a dielectric hydrometeor, for the second part of this dissertation we modify our streamer discharge model to accommodate an isolated dielectric particle representing the hydrometeor inside the computational region. Since the governing equations of the plasma discharge model are discretized on a uniform rectangular grid, the boundary cells do not conform to the shape of the dielectric. We utilize a boundary-cut cell method proposed by Ye et al. [1999] to handle these cut cells, and properly evaluate the corresponding fluxes. A boundary condition capturing method by Liu et al. [2000] has been used to properly enforce the electrostatic boundary conditions on the dielectric hydrometeor. The development of this model has enabled us to accurately simulate the discharges around dielectric hydrometeors with various shapes and physical states. Streamer discharge results obtained from the dielectric hydrometeor have been presented and compared with the results obtained from the first part of this work. We compare our modeling results with laboratory experiments and realistic thundercloud conditions and discuss the implications of this study to lightning initiation and other lightning related phenomena.

Download or read book Lightning written by Vladimir A. Rakov and published by Cambridge University Press. This book was released on 2003-08-04 with total page 734 pages. Available in PDF, EPUB and Kindle. Book excerpt: Table of contents

Download or read book Monthly Catalog of United States Government Publications written by and published by . This book was released on 1996 with total page 652 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Sprites Elves and Intense Lightning Discharges written by Martin Füllekrug and published by Springer Science & Business Media. This book was released on 2006-05-27 with total page 399 pages. Available in PDF, EPUB and Kindle. Book excerpt: Particularly intense lightning discharges can produce transient luminous events above thunderclouds, termed sprites, elves and jets. These short lived optical emissions in the mesosphere can reach from the tops of thunderclouds up to the ionosphere; they provide direct evidence of coupling from the lower atmosphere to the upper atmosphere. Sprites are arguably the most dramatic recent discovery in solar-terrestrial physics. Shortly after the first ground based video recordings of sprites, observations on board the Space Shuttle detected sprites and elves occurring all around the world. These reports led to detailed sprite observations in North America, South America, Australia, Japan, and Europe. Subsequently, sprites were detected from other space platforms such as the International Space Station and the ROCSAT satellite. During the past 15 years, more than 200 contributions on sprites have been published in the scientific literature to document this rapidly evolving new research area.

Download or read book Lightning written by Vladimir A. Rakov and published by Cambridge University Press. This book was released on 2007-01-08 with total page 1485 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lightning: Physics and Effects is the first book that covers essentially all aspects of lightning, including lightning physics, lightning protection and the interaction of lightning with a variety of objects and systems as well as with the environment. It is written in a style that will be accessible to the technical non-expert and is addressed to anyone interested in lightning and its effects. This will include physicists, engineers working in the power, communications, computer and aviation industries, meteorologists, atmospheric chemists, foresters, ecologists, physicians working in the area of electrical trauma and architects. This comprehensive reference volume contains over 300 illustrations, 70 tables containing quantitative information and a bibliography of more than 6000 references.

Download or read book Spring Meeting written by American Geophysical Union. Meeting and published by . This book was released on 1996 with total page 692 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Government Reports Announcements Index written by and published by . This book was released on 1996 with total page 668 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book FY 1995 Scientific and Technical Reports Articles Papers and Presentations Volume 1 written by and published by . This book was released on 1995 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Lightning Flash written by Vernon Cooray and published by IET. This book was released on 2003 with total page 600 pages. Available in PDF, EPUB and Kindle. Book excerpt: This unique book provides the reader with a thorough background in almost every aspect of lightning and its impact on electrical and electronic equipment. The contents range from basic discharge processes in air through transient electromagnetic field generation and interaction with overhead lines and underground cables, to lightning protection and testing techniques. This book is of value to anyone designing, installing or commissioning equipment which needs to be secured against lightning strikes, as well as being a sound introduction to research students working in the field.

Download or read book Electrical Processes in Atmospheres written by H. Dolezalek and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 875 pages. Available in PDF, EPUB and Kindle. Book excerpt: These Proceedings are published to give a full account of the Fifth International Conference on Atmospheric Electricity held in September 1974 in Garmisch-Partenkirchen in the Bavarian Alps in Germany. Traditionally, the Proceedings of these Conferences have served as reference books updating the textbooks and monographs on Atmospheric Electricity. As treated by these Conferences, Atmos pheric Electricity covers all aspects of this science, including the processes and problems which reach out into the Earth's environment as well as analogous processes on other planets and on the Moon. A history of these Conferences, an account of their purpose, and an outline of the scope and the preparation is to be found at the end of these Proceedings. There, also the Business Meetings of the involved organizations are mentioned. The Proceedings closely follow the original program and are accordingly organized into "Sessions". The papers printed in each "Session" in this book are the ones which were accepted for the sessions of the Conference with the same numbers and titles. Only the two "Special Sessions" have been given different numbers in the Proceedings, i.e. 2a and 10. In principle, all papers which were accepted by the Executive Panel either for full oral presentation or for printing in the Proceedings only, have in fact been included in these Proceedings, whether they were presented or not. In the latter case, a special note is made to explain the absence of a discussion.

Download or read book Lightning Protection of Aircraft written by Franklin Fisher and published by CreateSpace. This book was released on 2012-07-13 with total page 564 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is an attempt to present under one cover the current state of knowledge concerning the potential lightning effects on aircraft and that means that are available to designers and operators to protect against these effects. The impetus for writing this book springs from two sources- the increased use of nonmetallic materials in the structure of aircraft and the constant trend toward using electronic equipment to handle flight-critical control and navigation function.

Download or read book Chemical Kinetics Data Survey VII written by David Garvin and published by . This book was released on 1974 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book An Introduction to Lightning written by Vernon Cooray and published by Springer. This book was released on 2014-10-08 with total page 391 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book about lightning summarizes the essence of physics and effects of lightning in a non-technical manner and provides an up-to-date description of the phenomenon of lightning in simple language. Starting with the myths related to lightning, the reader is introduced to the mechanism of lightning flashes and their interactions with humans, human-made systems and Earth’s environment. Most of the available books on lightning are written for the experts in the field and there is a need for a book that introduces the undergraduate and beginning post graduate students to the subject of lightning and prepares them for more advanced books meant for the experts. This introductory book, which is based on a series of lectures given to undergraduate and postgraduate students in electrical engineering, is intended to fill this need. Tailored to the needs of university students who plan to study electrical engineering, meteorology, environmental or basic physics, it is also a valuable reference resource for laymen who are interested in knowing more on this phenomenon.