We present an alternative method for the exact calculations of the Wannier-Stark (WS) localization in a long periodic potential corresponding to a (50 Angstrom /30 Angstrom) GaAs/Ga0.7Al0.3As superlattice. We show that the electric field dependence of the electron wavefunction has unique localization dynamics. One interesting prediction is a small effect involving the change of the dipole field with increasing WS field. It is argued that this may give rise to parasitic effects in Bloch oscillations and, therefore, to noise in coherent terahertz emission. (C) 2001 Academic Press.