€All of the variability
in Polars occurs at a single period: the orbital period
–radial velocity
curves of the secondary
–X-ray light
curves from the primary
–polarisation
variations
Þthe
white dwarf/red dwarf are locked into the same orientation: synchronised rotation
€The mechanism for
synchronisation is the dissipation due to the magnetic field of the primary being dragged through the
secondary
€As relative spin rate
of primary decreases, locking can occur due to the dipole-dipole magnetostatic interaction between
primary and (weaker) secondary magnetic
field
€Some Polars not quite
in synchronism; in these systems it typically takes 5–50 days for white dwarf orientation to
repeat itself
€Very useful systems to
study the effect of orientation of magnetic field on the accretion process