  We propose a mechanism whereby spin supercurrents can be manipulated in
superconductor/ferromagnet proximity systems via nonequilibrium spin injection.
We find that if a spin supercurrent exists in equilibrium, a nonequilibrium
spin accumulation will exert a torque on the spins transported by this current.
This interaction causes a new spin supercurrent contribution to manifest out of
equilibrium, which is proportional to and polarized perpendicularly to both the
injected spins and equilibrium spin current. This is interesting for several
reasons: as a fundamental physical effect; due to possible applications as a
way to control spin supercurrents; and timeliness in light of recent
experiments on spin injection in proximitized superconductors.
