  A description of CMB temperature fluctuations beyond the power spectrum is
important for verifying models of structure formation, especially in view of
forthcoming high-resolution observations. We argue that higher-order statistics
of inter-scale correlations, because of their low cosmic variance, may be
effective in detecting non-Gaussian features in the CMB. Inter-scale
correlations are generically produced in defect-based models of structure
formation. We analytically study properties of general higher-order cumulants
of Fourier components of homogeneous random fields and design a new set of
statistics suitable for small-scale data analysis. Using simulated non-Gaussian
fields, we investigate the performance of the proposed statistics in presence
of a Gaussian background and pixel noise, using the bispectrum as the
underlying cumulant. Our numerical results suggest that detection of
non-Gaussian features by our method is reliable if the power spectrum of the
non-Gaussian components dominates that of the Gaussian background and noise
within at least a certain range of accessible scales.
