  We reanalyzed the c-type RR Lyrae star BE Dor (MACHO 5.4644.8,
OGLE-LMC-RRLYR-06002) that had been discovered to show cyclic period changes.
The photometric data of several sky surveys (DASCH, MACHO, OGLE, ASAS-SN, and
TESS) were used for analyses. The O-C diagram and pulsation period obtained
from Fourier analysis show significant period modulations in BE Dor. However,
different from the previous viewpoint, the changes are quasi-periodic and
abrupt. Therefore, the light-travel time effect caused by the companion motion
cannot explain the changes. Noting a same subtype star KIC 9453114 with similar
phenomena has a high macroturbulent velocity, and the degree of O-C changes
seem to be positively correlated with these velocities, we consider that the
mechanism leading to period modulation should be caused by the interaction
between turbulent convection and magnetic field activity in the ionization
zone, i.e., the viewpoint of Stothers. It may not explain the general Blazhko
effect but should explain such period modulations in BE Dor and those other
c-type RR Lyrae stars. We hope our discoveries and viewpoints can provide some
information and inspiration for relevant research.
