The polarity reversal of lightning‐generated sky wave

Hou, Wenhao (Key Laboratory of Meteorological Disaster, Ministry of Education (KLME)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disaster (CIC‐FEMD)/Key Laboratory for Aerosol‐Cloud‐Precipitation of China Meteorological Administration, Nanjing University of Information Science and Technology, Nanjing, China ; Electromagnetic Compatibility Laboratory, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland) ; Azadifar, Mohammad (School of Management and Engineering Vaud, HES-SO // University of Applied Sciences Western Switzerland) ; Rubinstein, Marcos (School of Management and Engineering Vaud, HES-SO // University of Applied Sciences Western Switzerland) ; Rachidi, Farhad (Electromagnetic Compatibility Laboratory, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland) ; Zhang, Qilin (Key Laboratory of Meteorological Disaster, Ministry of Education (KLME)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disaster (CIC‐FEMD)/Key Laboratory for Aerosol‐Cloud‐Precipitation of China Meteorological Administration, Nanjing University of Information Science and Technology, Nanjing, China)

The polarity reversal of the lightning‐generated first sky wave as a function of the observation distance is studied using a novel approach combining the finite‐difference time‐domain (FDTD) method and the superposition principle of electromagnetic waves. In this method, the sky wave is generated by radiation from the induced current produced by the motion of charged particles driven by the lightning‐radiated electromagnetic waves in the ionosphere. The horizontal and vertical components of the induced current density under the daytime and nighttime ionospheric conditions are evaluated. Their different contributions to the sky wave at different observation distances are analyzed in detail. Furthermore, a physical explanation for the polarity reversal in the time domain is proposed. It is found that, for relatively short observation distances (within ~200 km), the first sky wave is dominated by the component generated by the horizontal equivalent current in the Fresnel zone, while for longer observation distances (larger than ~300 km), the first sky wave is dominated by the component generated by the vertical equivalent current in the Fresnel zone. Since the polarities of the sky wave components generated by the vertical current source and horizontal current source are opposite, the polarity of the sky wave will reverse when increasing the observation distance.


Article Type:
scientifique
Faculty:
Ingénierie et Architecture
School:
HEIG-VD
Institute:
IICT - Institut des Technologies de l'Information et de la Communication
Date:
2020-06
Pagination:
29 p.
Published in:
Journal of Geophysical Research: Atmospheres
DOI:
ISSN:
2169-897X
Appears in Collection:



 Record created 2020-08-11, last modified 2020-10-27

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