Plasmoid is a key process for transferring magnetic flux and plasma in
planetary magnetospheres. At Earth，plasmoid is a key media transferring
energy and mass in the “Dungey Cycle” magnetospheric circulation. For
giant planets, plasmoid is primarily generated by the dynamic processes
associated with “Vasyliunas Cycle”. It is generally believed that
planetary magnetotails are favourable for producing plasmoids.
Nevertheless, recent study reveals that magnetic field lines could be
sufficiently stretched to allow magnetic reconnection (Guo et al. 2018a)
in Saturn’s dayside magnetodisc. And in the study, we report direct
observations of plasmoid in Saturn’s dayside magnetodisc. Moreover, we
perform a statistical investigation on the global plasmoid electron
density distribution. The results show an inverse correlation between
the nightside plasmoid electron density and local time, and the maximum
plasmoid electron density around prenoon local time on the dayside.
These results are consistent with the magnetospheric circulation picture
associated with“Vasyliunas Cycle”.