ISUAL‐Observed Blue Luminous Events: The Associated Sferics

The blue luminous events (BLEs) recorded by ISUAL (Imager of Sprites and Upper Atmospheric Lightning) radiate unambiguous middle ultraviolet to blue emissions (230–450 nm) but contain dim red emissions (623–754 nm). The BLE appears to be dot‐like on one ISUAL image with an integration time of 29 ms....

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Bibliographic Details
Published in:Journal of geophysical research. Space physics 2018-04, Vol.123 (4), p.3063-3077
Main Authors: Chou, Jung‐Kuang, Hsu, Rue‐Ron, Su, Han‐Tzong, Chen, Alfred Bing‐Chih, Kuo, Cheng‐Ling, Huang, Sung‐Ming, Chang, Shu‐Chun, Peng, Kang‐Ming, Wu, Yen‐Jung
Format: Article
Language:English
Subjects:
Blue jets (atmospherics)
Discharge
Emissions
ISUAL
jets
Lightning
Low frequencies
narrow bipolar events
Optical observations
Sferics
Sprites
Starters
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Summary:The blue luminous events (BLEs) recorded by ISUAL (Imager of Sprites and Upper Atmospheric Lightning) radiate unambiguous middle ultraviolet to blue emissions (230–450 nm) but contain dim red emissions (623–754 nm). The BLE appears to be dot‐like on one ISUAL image with an integration time of 29 ms. A few BLEs develop upward into blue jets/starters or type II gigantic jets (GJs). The associated sferics of the BLEs in the extremely low frequency to very low frequency band and in the low‐frequency band exhibit similar patterns to the narrow bipolar events (NBEs) identified in the very low frequency and low‐frequency band. The ISUAL BLEs are conjectured to be the accompanied light emissions of the NBEs. Both upward and downward propagating current obtained from the associated sferics of the BLEs have been found. The source heights of the six BLEs related to negative NBEs are estimated in the range of 16.2–17.8 km. These six events are suggested to occur between the upper positive charge layer and the negative screen charge layer on the top of the normally electrified thunderstorm. The six blue starters, one blue jet, and one type II GJ are inferred to be positive upward discharges from their associated sferics in the extremely low frequency to very low frequency band. Based on the simultaneous radio and optical observations, a NBE is conjectured to be the initiation discharge with rapidly flowing current within the thunderstorm, while a blue jet/starter or a type II GJ is suggested to be the ensuing discharge with slowly varying current propagating upward from the thunderstorm. Key Points ISUAL blue luminous events are the accompanied light emissions of narrow bipolar events A few BLEs related to negative NBEs develop upward and form the blue jets/starters or type II GJs A NBE is the initiation of the electrical discharge within thunderstorm, while an upward jet is the ensuing discharge
ISSN:2169-9380
2169-9402
DOI:10.1002/2017JA024793