  We experimentally identify the magnetostatic modes active for Brillouin light
scattering in the optical whispering gallery modes of a yttrium iron garnet
sphere. Each mode is identified by magnetic field dispersion of
ferromagnetic-resonance spectroscopy and coupling strength to the known field
distribution of the microwave drive antenna. Our optical measurements confirm
recent predictions that higher-order magnetostatic modes can also generate
optical scattering, according to the selection rules derived from the axial
symmetry. From this we summarize the selection rules for Brillouin light
scattering. We give experimental evidence that the optomagnonic coupling to
non-uniform magnons can be higher than that of the uniform Kittel mode.
