  Forthcoming datasets from the Planck experiment and others are in a position
to probe the CMB non-Gaussianity with higher accuracy than has yet been
possible and potentially open a new window into the physics of the very early
universe. However, a signal need not necessarily be inflationary in origin, and
possible contaminants should be examined in detail. One such is provided by
early universe magnetic fields, which can be produced by a variety of models
including during an inflationary phase, at phase transitions, or seeded by
cosmic defects. Should such fields have been extent in the early universe they
provide a natural source of CMB non-Gaussianity. Knowledge of the CMB angular
bispectrum requires the complete Fourier-space (or "intrinsic") bispectrum. In
this paper I consider in detail the intrinsic bispectra of an early-universe
magnetic field for a range of power-law magnetic power spectra.
