  Stochastic dynamics of a nonconserved scalar order parameter near its
critical point, subject to random stirring and mixing, is studied using the
field theoretic renormalization group. The stirring and mixing are modelled by
a random external Gaussian noise with the correlation function
$\propto\delta(t-t') k^{4-d-y}$ and the divergence-free (due to
incompressibility) velocity field, governed by the stochastic Navier--Stokes
equation with a random Gaussian force with the correlation function
$\propto\delta(t-t') k^{4-d-y'}$. Depending on the relations between the
exponents $y$ and $y'$ and the space dimensionality $d$, the model reveals
several types of scaling regimes. Some of them are well known (model A of
equilibrium critical dynamics and linear passive scalar field advected by a
random turbulent flow), but there are three new nonequilibrium regimes
(universality classes) associated with new nontrivial fixed points of the
renormalization group equations. The corresponding critical dimensions are
calculated in the two-loop approximation (second order of the triple expansion
in $y$, $y'$ and $\epsilon=4-d$).
