[MIS10-P03] Photodetachment of electrons at sprite altitudes by molecular nitrogen emissions as a mechanism of initiation of sprite streamers
Modeling and experimental findings indicate that the presence of plasma irregularities is a necessary condition for initiation of sprite streamers [e.g., Lang et al., JGR, 116, A10306, 2011; Qin et al., JGR, 116, A06305, 2011; GRL, 40, 4777, 2013; Nat. Comm., 5, 3740, 2014]. Sprite streamers are often preceded by a relatively low intensity diffuse glow discharge referred to as sprite halo [Barrington-Leigh et al., JGR, 106, 1741, 2001]. Janalizadeh and Pasko [Abstracts AE21A-08; AE21B-3132; presented at 2018 Fall Meeting, AGU, Washington DC, 10-14 Dec., 2018] introduced a framework allowing investigation of sprite streamer initiation as a result of electron impact ionization (due to lightning induced electric field) and photoionization (due to halo emissions) of small traces of metallic species deposited by meteoric trails. Furthermore, Janalizadeh and Pasko [Abstract AE31B-3105; presented at 2019 Fall Meeting, AGU, San Francisco CA, 9-13 Dec., 2019] have recently expanded this framework to studies of photodetachment of electrons from O-, O2-, OH- and NO3- ions. In the present work we expand on initial results reported at 2019 Fall AGU Meeting. In particular, we investigate streamer initiation from O2- ions, which possess the lowest electron affinity (i.e., 0.45 eV) among negative ions mentioned above [e.g., Phelps, Can. J. Chem., 47, 1783,1969; Pavlov, Surv. Geophys., 35, 259, 2014]. We also consider sequential sprite streamer initiation as a result of photodetachment from O- ions in more detail. Note that O- is the most abundantly produced negative ion in sprite streamers [Sentman et al., JGR, 113, D11112, 2008; Gordillo-Vazquez, J. Phys. D: Appl. Phys., 41, 234016, 2008] and may provide relatively long-lasting seeds for sequential initiation of sprite streamers. In addition to the first positive N2, second positive N2, first negative N2+, and Lyman-Birge-Hopfield (LBH) N2 band systems that have already been documented in sprites [e.g., Liu et al., GRL, 33, L01101, 2006, and references therein] and for which photodetachment has already been modeled [Janalizadeh and Pasko, Abstract AE31B-3105; presented at 2019 Fall Meeting, AGU, San Francisco CA, 9-13 Dec., 2019], we also consider photodetachment from aforementioned negative ions due to N2 band systems in the extreme ultraviolet spectral region, that has previously been discussed in the context of O2 photoionization in air [e.g., Zheleznyak et al., High Temp. 20, 357, 1982; Janalizadeh and Pasko, PSST, 28, 10, 105006, 2019].