  The spatial and spectral distributions of terahertz (THz) pulses emitted by
two-color air plasmas are theoretically investigated for focused laser pulses
and in the filamentation regime. We derive a so-called ''augmented'' conical
emission model, which, similarly to the one originally proposed by You et al.\
[Phys.\ Rev.\ Lett.\ {\bf 109}, 183902 (2012)], involves phase matching between
laser harmonics along the plasma channel, the plasma density and length, and
the emitted frequency as key parameters. Our augmented model, however, treats
envelope effects and accounts for transverse variations of both plasma- and
Kerr-driven potential THz emitters. We highlight the importance of the
characteristic spatio-spectral distributions of these two conversion mechanisms
in the expression of the angular radiated power. The results of our model are
successfully compared with data provided by a comprehensive, fully space and
time-resolved unidirectional solver. Importantly, these numerical simulations
clear up the effective plasma length along which THz emission develops,
compared with the dephasing length along which the laser fundamental and second
harmonic become out-of-phase. The impact of common optical aberrations, such as
sphericity, astigmatism, and coma, on the THz generation is also investigated.
Aberrations are shown to generally decrease the laser-to-THz conversion
efficiency and potentially induce spatial asymmetries and narrowing in the THz
spectra.
