  The FLUKA Monte Carlo program is used to calculate the effects of
hadroproduction by primary gamma rays incident upon the earth's atmosphere; for
the results presented in this paper, only primary angles at 0 degrees from
zenith are considered. The FLUKA code is believed to be quite accurate in
reproducing experimental photon hadroproduction data in the 1 GeV to 10 TeV
energy range studied. The charged pions which are so produced can decay to
muons with sufficient energy to reach ground level. The number of these muons
and their radial and energy distribution are studied for incident gamma ray
energies from 1 GeV to 10 TeV. The number of these muons is not negligible;
they can, in certain circumstances, be used to study potential sources of gamma
rays like gamma ray bursts. It is found, for example, that a 10 TeV incident
primary gamma ray produces, on average, 3.4 muons which reach ground level; the
gamma ray energy which produces the maximum number of muons at ground level
depends on the spectral index of the primary gamma spectrum, a constant which
describes how the primary gamma flux rises with decreasing primary energy. An
example: for a differential spectral index of 2.7, there is a broad maximum
number of muons coming from ~ 30 GeV primary gamma ray energy.
