  We examined the VSNET light curve of the ER UMa-type star V1159 Ori. We
detected a large variation of the supercycle (the interval between successive
superoutbursts) between extremes of 44.6 and 53.3 d. The outburst activity was
also found to decrease when the supercycle was long. The observed variation of
the supercycle corresponds to a variation of ~40 % of the mass-transfer rate
from the secondary star, totally unexpected for this class of objects. We also
detected a hint of ~1800 d periodicity in the variation, whose period is close
to what has been suggested for solar-type cycles for cataclysmic variables
(CVs). If this periodicity is caused by the magnetic activity of the secondary
star, this detection constitutes the first clear evidence of continuing
magnetic activity in CV evolution, even after crossing the period gap. This
activity may partly explain still poorly understood origins of the high
mass-transfer rates in ER UMa-type stars.
