Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The overall channels of the lightning discharges

07.11.2008
The VHF radio interferometer system was designed by ZHANG GuangShu, et al of Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences.

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!
Further information:
http://www.lzb.ac.cn

More articles from Earth Sciences:

nachricht New Study Will Help Find the Best Locations for Thermal Power Stations in Iceland
19.01.2017 | University of Gothenburg

nachricht Water - as the underlying driver of the Earth’s carbon cycle
17.01.2017 | Max-Planck-Institut für Biogeochemie

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>