  Mini-EUSO is a detector observing the Earth in the ultraviolet band from the
International Space Station through a nadir-facing window, transparent to the
UV radiation, in the Russian Zvezda module. Mini-EUSO main detector consists in
an optical system with two Fresnel lenses and a focal surface composed of an
array of 36 Hamamatsu Multi-Anode Photo-Multiplier tubes, for a total of 2304
pixels, with single photon counting sensitivity. The telescope also contains
two ancillary cameras, in the near infrared and visible ranges, to complement
measurements in these bandwidths. The instrument has a field of view of 44
degrees, a spatial resolution of about 6.3 km on the Earth surface and of about
4.7 km on the ionosphere. The telescope detects UV emissions of cosmic,
atmospheric and terrestrial origin on different time scales, from a few
micoseconds upwards. On the fastest timescale of 2.5 microseconds, Mini-EUSO is
able to observe atmospheric phenomena as Transient Luminous Events and in
particular the ELVES, which take place when an electromagnetic wave generated
by intra-cloud lightning interacts with the ionosphere, ionizing it and
producing apparently superluminal expanding rings of several 100 km and lasting
about 100 microseconds. These highly energetic fast events have been observed
to be produced in conjunction also with Terrestrial Gamma-Ray Flashes and
therefore a detailed study of their characteristics (speed, radius, energy...)
is of crucial importance for the understanding of these phenomena. In this
paper we present the observational capabilities of ELVE detection by Mini-EUSO
and specifically the reconstruction and study of ELVE characteristics.
