By using this system, a cloud-to-ground lightning flash containing 19 strokes was observed and several new characteristics of lightning have been revealed. The study is reported in volume51, number 5 (May, 2008) of the Science in China (Series D, Earth Sciences).
The system in this study has five antennas that form an array in orthogonal directions, and an interactive graphic analysis procedure is used to remove the fringe ambiguities. The system error, which comes from frequency conversion, is reduced by phase detection through direct high frequency amplifying. By using the system, the whole progression process in time and space of a lightning flash can be continuously reconstructed at microsecond orders. As an example, the overall channel of a normal cloud-to-ground lightning flash that contains 19 strokes was analyzed and presented. It is found that the preliminary breakdown event of the CG flash started from negative charge region and exhibited firstly a downward progression and then an upward propagation. Intense and continuous radiations during stepped leaders became much stronger when the first return stroke began. In contrast, there were less and only discrete radiations during dart leaders. Stepped leader and dart leader may transform to each other depending on the state of the ionization of the path. The progression speed of initial stepped leaders was about 105 ms-1, while that was about 4.1×106 ms-1 and 6.0×106 ms-1 for dart leaders and dart-stepped leaders, respectively. M events produced hook-shaped field changes, accompanied by active burst of radiations at their beginnings. Following these active radiation processes, M events appeared to contact finally into conducting main discharge channels. The mean progression speed of M events was about 7×107ms-1, greater than that of the dart leaders and dart-step leaders. K events and attempted leaders (ATP) were essentially the same as the dart leaders except that they could not reach the ground and initiate return strokes.
Two methods, time of arrival (TOA) technique and interferometric technique, have been used to locate RF radiation events of lightning discharge up to now. TOA technique works better for locating isolated, impulsive radiation events. Since TOA technique has less time resolution, it is impossible to use it to study the whole process of a lightning discharge in detail. Interferometric technique works better for burst of impulses lasting several tens or hundreds of microseconds and can be used to locate the whole process of a lighting discharge in a time resolution of microsecond orders. However, the existence of so-called fringe ambiguities severely limits the measurement precision. ZHANG GuangShu, et al., researchers of Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, have been studying the technique of the TOA and interferometer during the past 10 years and have successfully solved many problems of the previous systems.
Now, ZHANG GuangShu, et al. are working to combine various location methods in hope of developing a more powerful tool for lightning study.
Zhang GuangShu | EurekAlert!
UCI and NASA document accelerated glacier melting in West Antarctica
26.10.2016 | University of California - Irvine
Ice shelf vibrations cause unusual waves in Antarctic atmosphere
25.10.2016 | American Geophysical Union
Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.
This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...
Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion
Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
27.10.2016 | Materials Sciences
27.10.2016 | Physics and Astronomy
27.10.2016 | Life Sciences