Abstract
In this study, detection and three-dimensional (3D) imaging of lightning plasma channels are presented using radar interferometry. Experiments were carried out in Leshan, China with a 48.2 MHz VHF radar configured with an interferometric antenna array. The typical characteristics of lightning echoes are studied in the form of amplitude, phase, and doppler spectra derived from the raw in-phase/quadrature (I/Q) data. In addition, the 3D structure of lightning channels is reconstructed using the interferometry technique. The localization results of lightning are verified with the locating results of lightning detection networks operating at VLF ranges, which indicate the feasibility of using VHF radar for lightning mapping. The interpretation of the observational results is complicated by the dendric structure of lightning channel and the overlap between passive electromagnetic radiations and return echoes. Nevertheless, some parts of the characteristics of lightning are still evident. The observational result of return echoes shows good consistency with the overdense assumption of lightning channels. The transition from the overdense channel to the underdense channel in the form of amplitude and phase is clearly observed. This technique is very promising to reveal the typical characteristics of lightning return echoes and structure of lightning propagation processes.
Highlights
Lightning is an electrical discharge naturally occurring between charge regions of opposite polarities inside thunderclouds or between clouds and the ground, accompanying electromagnetic radiations over a wide range of frequencies during the formation of hot ionized plasma channels and visible luminous flashes [1,2]
We investigate the characteristics of lightning return echoes and reconstruct the 3D structure of lightning channels using the VHF radar with interferometric antenna configuration in Leshan, China
The intensity of lightning return echoes backscattered by by ionized channels significantly stronger than background noises ampliionized channels areare significantly stronger than thethe background noises andand the the amplitude tude of passive electromagnetic emissions produced by the breakdown and ionization of passive electromagnetic emissions produced by the breakdown and ionization processes processes are higher than that of noises
Summary
Lightning is an electrical discharge naturally occurring between charge regions of opposite polarities inside thunderclouds or between clouds and the ground, accompanying electromagnetic radiations over a wide range of frequencies during the formation of hot ionized plasma channels and visible luminous flashes [1,2]. To protect human life and assets from damage caused by the massive amount of energy released by lightning, lightning detection and localization methods and studies of lightning characteristics are of great significance [2,3,4,5]. Radar, photographic instruments such as high-speed video camera, acoustic array, passive spheric detection system, and electrostatic field sensor are the common instruments for the study of lightning. The configuration of HSV and transmission grating can be implemented to set up the spectral recording system in order to measure the temperature and radius of lightning channel [8]
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