The Galactic Kinematics of Cataclysmic Variables
  Kinematical properties of CVs were investigated according to population types
and orbital periods, using the space velocities computed from recently updated
systemic velocities, proper motions and parallaxes. Reliability of collected
space velocity data are refined by removing 34 systems with largest space
velocity errors. The 216 CVs in the refined sample were shown to have a
dispersion of $53.70 \pm 7.41$ km s$^{-1}$ corresponding to a mean kinematical
age of $5.29 \pm 1.35$ Gyr. Population types of CVs were identified using their
Galactic orbital parameters. According to the population analysis, seven old
thin disc, nine thick disc and one halo CV were found in the sample, indicating
that 94% of CVs in the Solar Neighbourhood belong to the thin-disc component of
the Galaxy. Mean kinematical ages $3.40 \pm 1.03$ and $3.90 \pm 1.28$ Gyr are
for the non-magnetic thin-disc CVs below and above the period gap,
respectively. There is not a meaningful difference between the velocity
dispersions below and above the gap. Velocity dispersions of the non-magnetic
thin-disc systems below and above the gap are $24.95 \pm 3.46$ and $26.60 \pm
4.18$ km s$^{-1}$, respectively. This result is not in agreement with the
standard formation and evolution theory of CVs. The mean kinematical ages of
the CV groups in various orbital period intervals increase towards shorter
orbital periods. This is in agreement with the standard theory for the
evolution of CVs. Rate of orbital period change was found to be
$dP/dt=-1.62(\pm 0.15)\times 10^{-5}$ sec yr$^{-1}$.
