Inclusion of complete ion chemistry in the calculation of minor species production during energetic particle deposition events leads to significant enhancement in the calculated nitric acid concentration during precipitation. An ionization rate of 1.2¿103 cm-3 s-1 imposed for 1 day increases HNO3 from 3¿105 to 6¿107 cm-3 at 50 km. With an ionization rate of 600 cm-3 s-1, the maximum HNO3 is 3¿107 cm-3. Calculations which neglect negative ions predict that nitric acid will fall during precipitation events. The decay time for converting HNO3 into odd nitrogen and hydrogen is more than 1 day for equinoctial periods at 70¿ latitude. Examination of nitric acid data should yield important information on the magnitude and frequency of charged particle events.