  Gamma-ray continuum at > 10 MeV photon energy yields information on > 0.2 -
0.3 GeV/nucleon ions at the Sun. We use the general-purpose Monte Carlo code
FLUKA (FLUktuierende KAskade) to model the transport of ions injected into
thick and thin target sources, the nuclear processes that give rise to pions
and other secondaries and the escape of the resulting photons from the
atmosphere. We give examples of photon spectra calculated with a range of
different assumptions about the primary ion velocity distribution and the
source region. We show that FLUKA gives results for pion decay photon
emissivity in agreement with previous treatments. Through the directionality of
secondary products, as well as Compton scattering and pair production of
photons prior to escaping the Sun, the predicted spectrum depends significantly
on the viewing angle. Details of the photon spectrum in the 100 MeV range may
constrain the angular distribution of primary ions and the depths at which they
interact. We display a set of thick-target spectra produced making various
assumptions about the incident ion energy and angular distribution and the
viewing angle. If ions are very strongly beamed downward, or ion energies do
not extend much above 1 GeV/nucleon, the photon spectrum is highly insensitive
to details of the ion distribution. Under the simplest assumptions, flares
observed near disc centre should not display significant radiation above 1 GeV
photon energy. We give an example application to Fermi Large Area Telescope
data from the flare of 12 June 2010.
