Short Light Transients and millisecond-scale follow-up emissions observed by Mini-EUSO

Mini-EUSO is a space-based ultraviolet telescope operating aboard the International Space Station since 2019 as part of the JEM-EUSO Programme. The instrument monitors the Earth’s night-time atmosphere in the 290–430 nm wavelength range with a temporal resolution of 2.5 μs and a ground spatial resolution of approximately 5–6 km. In addition to its high time resolution, Mini-EUSO combines imaging capabilities with high sensitivity, enabled by a 25 cm diameter optical system, allowing the detection of fast and faint UV emissions associated with atmospheric electrical activity.

In this contribution, we present the analysis of a population of fast, short-duration UV transients, referred to as Short Light Transients (SLTs), with typical timescales between 100 μs and 200 μs detected by Mini-EUSO. These events are stationary within the spatial resolution of the detector and are frequently followed, at the same geographical location, by additional atmospheric emissions occurring within 1–200 ms. The observed temporal correlations and spatial localization suggest a connection with rapid atmospheric electrical processes, potentially related to lightning activity or to early-stage or precursor phenomena associated with transient luminous events.

The combination of microsecond-scale temporal resolution, imaging capability, and high optical sensitivity makes Mini-EUSO particularly well suited for the investigation of fast, localized UV emissions that are challenging to observe with conventional lightning and atmospheric monitoring instruments.
In addition to the SLTs discussed here, Mini-EUSO has recorded a wide range of lightning-related and transient luminous phenomena, highlighting the potential of space-based UV observations for the study of fast electrical processes in the atmosphere.