  Chromospheric swirls are the observational signatures of rotating magnetic
field structures in the solar atmosphere, also known as magnetic tornadoes.
Swirls appear as dark rotating features in the core of the spectral line of
singly ionized calcium at a wavelength of 854.2 nm. This signature can be very
subtle and difficult to detect given the dynamic changes in the solar
chromosphere. Important steps towards a systematic and objective detection
method are the compilation and characterization of a statistically significant
sample of observed and simulated chromospheric swirls. Here, we provide a more
exact definition of the chromospheric swirl phenomenon and also present a first
morphological classification of swirls with three types: (I) Ring, (II) Split,
(III) Spiral. We also discuss the nature of the magnetic field structures
connected to tornadoes and the influence of limited spatial resolution on the
appearance of their photospheric footpoints.
