  We report results of polarimetric observations of comet 21P/Giacobini-Zinner
made at phase angles, {\alpha}=76-78 deg, between 10 and 17 of September 2018,
and compare them with previous measurements. We find significant variations in
the polarimetric signals that appear consistent with those reported previously.
These variations and subsequent modeling suggest that the particles in the coma
are replenished within a period of approximately one day. This period is
significantly shorter for highly absorbing carbonaceous particles than for
non-absorbing Mg-rich silicate particles. Such a difference in the relative
abundances of these components can lead to variations in the polarization
response of the coma. The strong positive polarization in the subsolar
direction suggests a large relative abundance of carbonaceous material, which
may be an indicator of jet-type activity.
