  We evaluate the effects of high-energy ionizing particles on the Si:As
impurity band conduction (IBC) mid-infrared detector on board AKARI, the
Japanese infrared astronomical satellite. IBC-type detectors are known to be
little influenced by ionizing radiation. However we find that the detector is
significantly affected by in-orbit ionizing radiation even after spikes induced
by ionizing particles are removed. The effects are described as changes mostly
in the offset of detector output, but not in the gain. We conclude that the
changes in the offset are caused mainly by increase in dark current. We
establish a method to correct these ionizing radiation effects. The method is
essential to improve the quality and to increase the sky coverage of the AKARI
mid-infrared all-sky-survey map.
