  The breakdown of statistical homogeneity and isotropy of cosmic perturbations
is a generic feature of ultra large scale structure of the cosmos, in
particular, of non trivial cosmic topology. The statistical isotropy (SI) of
the Cosmic Microwave Background temperature fluctuations (CMB anisotropy) is
sensitive to this breakdown on largest scales comparable to, and even beyond
the cosmic horizon. We study a set of measures, $\kappa_\ell$ ($\ell=1,2,3,
>...$) which for non-zero values indicate and quantify statistical isotropy
violations in a CMB map. The main goal here is to interpret the $\kappa_\ell$
spectrum and relate it to characteristic patterns in the correlation function
of CMB anisotropy arising from cosmic topology. We numerically compute the
predicted $\kappa_\ell$ spectrum for CMB anisotropy in flat torus universe
models. The essential features are captured in the leading order approximation
to the correlation function where $\kappa_\ell$ can be calculated analytically.
The $\kappa_\ell$ spectrum is shown to reflect the number, importance and
relative orientation of principal directions in the CMB correlation dictated by
the shape of the Dirichlet domain (DD) of the compact space and its size
relative to cosmic horizon. Hence, besides detecting cosmic topology,
$\kappa_\ell$ can discriminate between different topology of the universe
complementing ongoing search for cosmic topology in CMB anisotropy data.
