  The terrestrial effects of major solar events such as the Carrington
white-light flare and subsequent geomagnetic storm of August-September 1859 are
of considerable interest, especially in light of recent predictions that such
extreme events will be more likely over the coming decades. Here we present
results of modeling the atmospheric effects, especially production of odd
nitrogen compounds and subsequent depletion of ozone, by solar protons
associated with the Carrington event. This study combines approaches from two
previous studies of the atmospheric effect of this event. We investigate
changes in NOy compounds as well as depletion of O3 using a two-dimensional
atmospheric chemistry and dynamics model. Atmospheric ionization is computed
using a range-energy relation with four different proxy proton spectra
associated with more recent well-known solar proton events. We find that
changes in atmospheric constituents are in reasonable agreement with previous
studies, but effects of the four proxy spectra used vary more widely than found
by one of those studies. In particular, we find greater impact for harder
proton spectra, given a constant total fluence. We report computed nitrate
deposition values and compare to measured values in ice cores. Finally, we
briefly investigate the impact of the modeled ozone depletion on surface-level
solar ultraviolet radiation.
