  Detailed understanding of the ionization process in noble liquid detectors is
important for their use in applications such as the search for dark matter and
coherent elastic neutrino-nucleus scattering. The response of noble liquid
detectors to low-energy ionization events is poorly understood at this time. We
describe a new simulation tool which predicts the ionization yield from
electronic energy deposits (E < 10keV) in liquid Ar, including the dependence
of the yield on the applied electric drift field. The ionization signal
produced in a liquid argon detector from $^{37}$Ar beta decay and $^{55}$Fe
X-rays has been calculated using the new model.
