Streamer initiation from column hydrometeor at weak ambient electric field

On the Emergence Mechanism of Carrot Sprites

“…Nowadays it is accepted that sprites originate from a quasi-electrostatic field produced by uncompensated electric charges due to lightning in the troposphere (Pasko et al, 1995(Pasko et al, , 1997. Several works (Köhn et al, 2019;Liu et al, 2015;Luque & Ebert, 2009;Wu et al, 2019) point out to the presence of inhomogeneities as a requirement for the initiation sprite streamers.…”

Study on Dominant Parameters Determining Streamer Initiation From Hydrometeors in Thundercloud Fields

“…All simulations in this study choose the same ratio for hydrometeors with different column radius. Wu, Gao, Ma, & Liu (2019) have proved that a column hydrometeor without charge can initiate a streamer at a minimum field of 0.5 E k , and we have calculated the corresponding Meek number for this case is approximately 17, a value slightly lower than that obtained for spherical hydrometeor without charge. Therefore, we choose Meek number 17 to draw the line to show the relation between critical field and radius of column hydrometeors as in Figure 5.…”

“…The secondary-electron emissions are therefore not taken into account. Electron reflection is calculated based on the formula discussed in Wu, Gao, Ma, and Liu (2019). As used in Sadighi et al (2015) and Wu, Gao, Ma, and Liu (2019), the simulation domain is chosen at 7 km altitude which is a typical lightning trigger altitude (Marshall et al, 2005) and where the breakdown threshold field of air E k ≈ 1.446 × 10 6 V/m.…”

“…Sadighi et al (2015) showed that a streamer can be initiated from an isolated ionization column with a length of 6.6 mm and radius of 0.75 mm and peak density of 2 × 10 19 m −3 in 0.3 E k . There are some difference between the real hydrometeors with rigid physical interface and the ionization column (Gao et al, 2020;Ma et al, 2021;Wu, Gao, Ma, & Liu, 2019). Such as the ionization column has no rigid interface, and electrons can pass through it freely without gathering on its surface.…”

“…To better simulate real hydrometeors, the researchers have developed a dielectric model with rigid interface to study streamer inception. Wu, Gao, Ma, and Liu (2019) simulated a streamer discharge used a dielectric column with a length 11 mm and a radius of 1.1 mm in 0.5 E k at 7 km altitude. Similarly, using the dielectric model, Dubinova et al (2015) simulated streamers initiation from large hydrometeors.…”