  The effect of poloidal asymmetry of impurities on impurity transport driven
by electrostatic turbulence in tokamak plasmas is analyzed. It is found that in
the presence of in-out asymmetric impurity populations the zero-flux impurity
density gradient (the so-called peaking factor) is significantly reduced. A
sign change in the impurity flux may occur if the asymmetry is sufficiently
large. This may be a contributing reason for the observed outward convection of
impurities in the presence of radio frequency heating. The effect of in-out
asymmetry is most significant in regions with low temperature gradients. In the
trapped electron mode dominated case also an up-down asymmetry can lead to a
sign change in the peaking factor from positive to negative. The effect of ion
parallel compressibility on the peaking factor is significant, and leads to
positive peaking factors in regions with high temperature gradients, even in
the presence of in-out asymmetry.
