  Spacecraft observations showed that electron heat conduction in the solar
wind is probably regulated by whistler waves, whose origin and efficiency in
electron heat flux suppression is actively investigated. In this paper, we
present Particle-In-Cell simulations of a combined whistler heat flux and
temperature anisotropy instability that can operate in the solar wind. The
simulations are performed in a uniform plasma and initialized with core and
halo electron populations typical of the solar wind. We demonstrate that the
instability produces whistler waves propagating both along (anti-sunward) and
opposite (sunward) to the electron heat flux. The saturated amplitudes of both
sunward and anti-sunward whistler waves are strongly correlated with their {\it
initial} linear growth rates, $B_{w}/B_0\sim (\gamma/\omega_{ce})^{\nu}$, where
for typical electron betas we have $0.6\lesssim \nu\lesssim 0.9$. The
correlations of whistler wave amplitudes and spectral widths with plasma
parameters (electron beta and temperature anisotropy) revealed in the
simulations are consistent with those observed in the solar wind. The
efficiency of electron heat flux suppression is positively correlated with the
saturated amplitude of sunward whistler waves. The electron heat flux can be
suppressed by 10--60% provided that the saturated amplitude of sunward whistler
waves exceeds about 1% of background magnetic field. Other experimental
applications of the presented results are discussed.
