  High-z Type Ia supernovae are expected to be gravitationally lensed by the
foreground distribution of large-scale structure. The resulting magnification
of supernovae is statistically measurable, and the angular correlation of the
magnification pattern directly probes the integrated mass density along the
line of sight. Measurements of cosmic magnification of supernovae therefore
complements galaxy shear measurements in providing a direct measure of
clustering of the dark matter. As the number of supernovae is typically much
smaller than the number of sheared galaxies, the two-point correlation function
of lensed Type Ia supernovae suffers from significantly increased shot noise.
Neverthless, we find that the magnification map of a large sample of
supernovae, such as that expected from next generation dedicated searches, will
be easily measurable and provide an important cosmological tool. For example, a
search over 20 sq. deg. over five years leading to a sample of ~ 10,000
supernovae would measure the angular power spectrum of cosmic magnification
with a cumulative signal-to-noise ratio of ~20. This detection can be further
improved once the supernova distance measurements are cross-correlated with
measurements of the foreground galaxy distribution. The magnification maps made
using supernovae can be used for important cross-checks with traditional
lensing shear statistics obtained in the same fields, as well as help to
control systematics. We discuss two applications of supernova magnification
maps: the breaking of the mass-sheet degeneracy when estimating masses of
shear-detected clusters, and constraining the second-order corrections to weak
lensing observables.
