On negative Sprites and the Polarity Paradox

Abstract

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.

Negative Streamer Initiation From an Isolated Hydrometeor in a Subbreakdown Electric Field

“…Sprites are electrical discharges above thunderstorms, caused by the electric field generated by intense cloud‐to‐ground lightning flashes (Pasko, 2010). Negative sprites initiated by negative streamers have been observed (Barrington‐Leigh et al., 1999; Boggs et al., 2016; Chen et al., 2019; Taylor et al., 2008) but are much rarer than positive sprites. In addition, a positive sprite is always initiated by positive streamers that propagate downward, and upward propagating negative streamers may be initiated later, with a significant delay (Stenbaek‐Nielsen, & McHarg, 2008).…”

Ground Observation of Negative Sprites Over a Tropical Thunderstorm as the Embryo of Hurricane Harvey (2017)

“…However, tropical cyclones are not frequent oceanic meteorological systems. A significant proportion of negative sprites were observed by space‐borne platforms in oceanic thunderstorms (e.g., Chen et al., 2019; Lu et al., 2017). Williams et al.…”

“…Although more than 90% of lightning occurs over land (Christian et al, 2003), the satellite observations indicate that sprites that occurred over oceanic thunderstorms show a fairly high proportion of negative sprites (Chen et al, 2008(Chen et al, , 2019Lu et al, 2017), which could be attributed to the fact that oceanic thunderstorms are more efficient in producing CG strokes with high peak currents as well as large charge moment change than their continental counterpart (Chronis et al, 2016;Said et al, 2013). Negative sprites and their parent CG lightning in the ocean are still not well understood in many ways.…”

Space‐Based Observation of a Negative Sprite With an Unusual Signature of Associated Sprite Current

“…For the red sprites observed over continental thunderstorms, the vast majority are produced by positive CG strokes (e.g., Li et al., 2012), and those events appearing to be particularly bright could drive a remarkable signature called “sprite current” in sprite‐associated broadband lightning sferics (Cummer et al., 1998; Hager et al., 2012). Ground‐based observations show that Only a very small fraction (less than 1%) is generated by negative lightning strokes (Lu et al., 2013; Williams et al., 2012), while the observations of the Imager of Sprites and Upper Atmospheric Lightning (ISUAL) aboard the FORMOSAT‐2 satellite indicate that the proportion can reach up to nearly 20% over oceanic thunderstorms (Chen et al., 2019; Lu et al., 2017).…”