  The Infrared Array Camera (IRAC) is a four-channel camera on the Spitzer
Space Telescope, one of three focal plane science instruments. IRAC uses two
pairs of 256x256 pixel InSb and Si:As IBC detectors to provide simultaneous
imaging at 3.6, 4.5, 5.8, and 8 microns. IRAC experiences a flux of cosmic rays
and solar protons that produce transient effects in science images from each of
the arrays, with 4-6 pixels per second being affected during each integration.
During extreme solar flares, IRAC experiences a much higher rate of transients
which affects the science data quality. We present cosmic ray rates and
observed detector characteristics for IRAC during the first two years of
science operation, and rates observed in a period of elevated solar proton flux
during an intense solar flare in January 2005. We show the changes to the IRAC
detectors observed since launch, and assess their impacts to the science data
quality.
