We suggest a possible mechanism for enhancement of erbium luminescence in crystalline silicon by terahertz (THz) radiation under conditions of constant band-to-band pumping. The suggested mechanism consists of Auger excitation of an Er3+ ion into the second excited state by recombination of an electron-hole pair assisted by THz radiation. After the excitation Er3+ ion undergoes nonradiative relaxation into the first exited state, from which the radiative transition takes place. We estimate the value of the excitation probability for reasonable experimental parameters and show that the excitation process has a strong dependence on the frequency of the THz radiation and may be observed for frequencies in the range of 15-35 THz. (C) 2003 Elsevier Science B.V. All rights reserved.