  The electric current helicity density $\displaystyle
\chi=\langle\epsilon_{ijk}b_i\frac{\partial b_k}{\partial x_j}\rangle$ contains
six terms, where $b_i$ are components of the magnetic field. Due to the
observational limitations, only four of the above six terms can be inferred
from solar photospheric vector magnetograms. By comparing the results for
simulation we distinguished the statistical difference of above six terms for
isotropic and anisotropic cases. We estimated the relative degree of anisotropy
for three typical active regions and found that it is of order 0.8 which means
the assumption of local isotropy for the observable current helicity density
terms is generally not satisfied for solar active regions. Upon studies of the
statistical properties of the anisotropy of magnetic field of solar active
regions with latitudes and with evolution in the solar cycle, we conclude that
the consistency of that assumption of local homogeneity and isotropy requires
further analysis in the light of our findings.
