Modeling Whistlers Generated by Gigantic Jets and a Case Study

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Title:	Modeling Whistlers Generated by Gigantic Jets and a Case Study
Authors:	汪愷悌;張淑鈞;黃崧銘;許瑞榮;Berthlier, J. J.;Onishi, T.
Date:	2016-02-28
Issue Date:	2016-04-27 11:26:28 (UTC+8)
Abstract:	This is the first attempt to model the characteristics of whistlers generated from a gigantic jet (GJ) as well as to examine satellite observations and find the existence of such type of whistlers. Modeling is based on disturbances in the electric field, as measured by NCKU ELF/VLF station, associated with a representative tree-like GJ event over typhoon Lionrock. The power spectrum of observed GJ differs from that of common cloud-to-ground lightning in its primary intensities below a few kHz and an initiating lightning on a wider frequency range. Therefore, the calculated frequency-time spectrogram shows two sequent whistlers, with the later one emitted mainly below a few kHz. Detectability is evaluated by considering the absorption of amplitudes resulted from particle collisions associated with the propagation of generated waves. Our results show that the waves are subject to greater attenuation as the frequency increases; however, a reversal occurs at lower frequencies of a few hundred Hz due to ion effects. Differences between GJ-generated signals and common lightning-generated whistlers are also explored in order to distinguish them in observational data. The electric fields observed by DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) satellite mission are then investigated based on the locations of tree-like GJ events observed by ISUAL (Imager of Sprites and Upper Atmospheric Lightning). Paired whistlers, detected right after the tree-like GJ event occurred closest to the satellite location among all examined events, with power distribution features on the frequency-time spectrogram resembling modeled two sequent whistlers, is found.
Relation:	2016大氣科學學門研究成果發表會電子論文集
Appears in Collections:	[Graduate Institute & Department of Aerospace Engineering] Proceeding

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