  Measurements of the background intensity and polarization of the twilight sky
were conducted during the "purple lights" epoch that was potentially caused by
the Raikoke volcano eruption in the summer of 2019. An increase in sky
brightness paired with a decrease in polarization was registered, especially
noticeable in the dusk segment. Using techniques developed in previous works,
altitude distribution and the mean particle size of additional aerosol was
found. The mean radius of (0.11 micrometers) is typical for background or
moderate eruption conditions, however, aerosols were mostly observed in the
upper troposphere and near the tropopause rather than in the stratosphere. A
comparison with existing aerosol data after mid-latitude eruptions like the
Kasatochi volcano eruption one decade ago showed similar properties, which can
be used as confirmation that the "purple lights" event in 2019 was of volcanic
nature.
