“…Each of these types of phenomena exhibits a different morphology but they likely share common physical processes. The blue color indicates the presence of electron‐impact excitation of molecular nitrogen (Gordillo‐Vázquez & Pérez‐Invernón, 2021; Pasko, 2008; Surkov & Hayakawa, 2020) and the weak or absent atomic oxygen line at 777.4 nm, indicates that air does not reach high temperatures, typically associated with lightning leaders at ground level. This points to streamer coronas being the key component of BLUEs, a conclusion supported by the close association between BLUEs and narrow bipolar events (NBEs) (F. Liu et al., 2018; Soler et al., 2020), which are radio emissions also attributed to corona discharges in thunderclouds (N. Liu et al., 2019; Rison et al., 2016; Tilles et al., 2019).…”