Analysis of lightning strokes associated with sprites observed by ISUAL in the vicinity of North America

Self Cite

On 19 August 2012, the Imager of Sprites and Upper Atmospheric Lightning on board the FORMOSAT‐2 satellite captured a sequence of seven blue discharges within 1 min that emanated from a parent thunderstorm over Lake Taihu in East China. The analysis of lightning activity produced in the thunderstorm indicates that at least six of these events occurred in association with negative narrow bipolar events (NBEs) that were concurrent with the blue discharge by less than 1 ms, and negative cloud‐to‐ground occurred within 6 s before each blue discharge, which is in agreement with the modeling presented by Krehbiel et al. (2008). Therefore, the frequent occurrence of negative cloud‐to‐ground could provide the favorable condition for the production of blue discharges, and negative NBEs are probably the initial event of blue discharges. The detection of negative NBEs might provide a convenient approach to detect the occurrence of blue discharges as lightning bolt shooting upward from the top of energetic thunderstorms.

Section: Observations and Datamentioning

confidence: 97%

Observations of Blue Discharges Associated With Negative Narrow Bipolar Events in Active Deep Convection

Liu

Zhu

et al. 2018

Self Cite

“…However, the correction factors proposed in Hsu et al (2008) to compensate for the instrument sensitivity and other observational shortfalls are rather speculative, since their raw occurrence rates, 0.47 and 0.37 events/min respectively for sprites and halos, are very similar. Lu et al (2017 and investigated the lightning strokes associated with ISUAL sprites and halos in North America. The results indicate that the percentage of negative sprites is significant (~18%), and they usually accompany halos and predominantly occur over oceanic as well as coastal thunderstorms.…”

Section: 1029/2019gl083804mentioning

confidence: 99%

“…Lu et al ( and ) investigated the lightning strokes associated with ISUAL sprites and halos in North America. The results indicate that the percentage of negative sprites is significant (~18%), and they usually accompany halos and predominantly occur over oceanic as well as coastal thunderstorms.…”

Section: Introductionmentioning

confidence: 99%

On negative Sprites and the Polarity Paradox

Chen

Chuang

et al. 2019

Self Cite

Energetic positive and negative cloud‐to‐ground (CG) flashes are both capable of producing sprites. Negative CGs typically outnumber the positive ones by 10 to 1. However, >99.9 % of reported sprites were found to be initiated by positive CGs—thus the polarity paradox. Here, sprites recorded by the Imager of Sprites and Upper Atmospheric Lightning (ISUAL) mission were analyzed along with extremely low‐frequency band magnetic field data to resolve this paradox. Approximately twenty‐five percent of the sprites are found to be associated with negative CG lightning. “Negative” sprites mainly congregate in the latitudinal regions below 20°, while positive sprites scatter up to 50°. The ISUAL negative sprites are evidently beyond the observable ranges of the ground sites reported in previous studies. Hence, the sprite polarity paradox is likely a selection effect of the middle‐ to high‐altitudinal observation sites. The charge moment changes and accompanying transient luminous events of sprites were also examined and found to be polarity dependent.

“…Sprites produced by negative CGs are very rare in the land areas (Li et al, ), which has been largely attributed to the lack of sufficiently strong negative strokes (with large iCMCs) produced by continental thunderstorms (Cummer & Lyons, ). The observations of sprites on the spaceborne platform ISUAL during a 12‐year period (2004–2015) suggest that a significant proportion (>80%) of negative sprites were produced in tropical oceanic/coastal thunderstorms (Lu et al, ). In particular, in the vast oceanic area to the north of Venezuela, only negative sprites have been observed, which is also shown by Williams et al (; Figure ).…”

Section: Why No Observation Of Negative Sprites?mentioning

confidence: 99%

“…The occurrence of sprites is the consequence of conventional dielectric breakdown that persists for a sufficiently long time so that there is considerable development of streamers (Liu et al, ; Qin et al, ). Although the minimum iCMC for triggering negative sprites is estimated to be −320 C‐km (Qin et al, ), the iCMC produced by negative sprite‐producing CG strokes usually exceeds −450 C‐km (Boggs et al, ; Li et al, ), which is much higher than the typical threshold (around +300 C‐km) for positive sprite‐producing iCMCs (e.g., Lu et al, ). The streamers of negative sprites are usually dim and terminate at relatively high altitude (Li et al, ), indicating the excitation by a lightning current with relatively short timescale (<0.5 ms for the cases examined by Li et al, , and Liu et al, ).…”

Section: Why No Observation Of Negative Sprites?mentioning

confidence: 99%

Observations of Red Sprites Above Hurricane Matthew

Huang

Yue

et al. 2018

Self Cite

More than three dozen red sprites were captured above Hurricane Matthew on the nights of 1 and 2 October 2016 as it passed to the north of Venezuela after undergoing rapid intensification. Analyses using broadband magnetic fields indicate that all of the sprites were produced by positive cloud‐to‐ground (CG) strokes located within the outer rainbands as defined by relatively cold cloud top brightness temperatures (≤194 K). Negative CG strokes with impulse charge transfers exceeding the threshold of sprite production also existed, but the timescale of the charge transfer was not sufficiently long to develop streamers. The reported observations are contrary to the finding of the Imager of Sprites/Upper Atmospheric Lightning showing that sprites are preferentially produced by negative strokes in the same geographic region. Further ground‐based observations are desired to obtain additional insights into the convective regimes associated with the dominance of negative sprites in many oceanic and coastal thunderstorms.