A nightsky optical phenomenon named Strong Thermal Emission Velocity Enhancement (STEVE) has been a topic of great research interest in the past 1-2 years. Its presence was reported in the literature over a century ago (see a historical review by Hunnekuhl and MacDonald [2020]), but escaped the attention of scientists for a long time, until it was brought forth again by citizen scientists and auroral photography enthusiasts in recent years. To date, while its generation mechanism remains unknown, some important advancements have been made toward the understanding of STEVE. (1) STEVE is located equatorward of traditional auroras, and there has been no evidence of appreciable electron/proton precipitation that could be the cause of the luminosity (Gallardo-Lacourt et al., 2018a, 2018b; MacDonald et al., 2018), suggesting that STEVE is not traditional aurora. (2) STEVE is found to be co-located with strong ionospheric electron heating and fast subauroral ion drifts (SAID) in joint optical and in situ satellite observations (Archer et al., 2019a; Chu et al., 2019; MacDonald et al., 2018; Nishimura et al., 2019; 2020a). (3) STEVE occurs during substorm intervals, and typically starts to emerge ∼1 h after the substorm onset (Gallardo-Lacourt et al., 2018a). (4) The emission altitude of STEVE is typically at ∼210-260 km, though sometimes a separate yet weaker STEVE arc may co-exist at lower altitude (Archer et al., 2019b; Hunnekuhl and MacDonald 2019; Liang et al., 2019). (5) Recently, using spectrograph data it was unveiled that STEVE's main source of brightness comes from an overall enhancement of a continuous visual spectrum, that is, an airglow continuum (AGC, Gillies et al., 2019; Liang et al., 2019), with small or none out-of-background green-line 557.7 nm emissions contained in the STEVE spectrum. While the existence of night AGC has been known for decades (Barbier et al., 1951), their commonly reported intensities in the existing literature (e.g. Sternberg &