  We investigate the effect of Coulomb drag resistance in a bilayer system of
strongly-correlated electron liquids magnetized by an in-plane field employing
the framework of hydrodynamic theory. We identify a mechanism for drag
magnetoresistance, which physically arises from the spin diffusion driven by
fluctuations of the spin currents within a partially spin-polarized fluid. This
effect is further enhanced by acoustic and optic plasmon resonances within the
bilayer, where hydrodynamic plasmons are driven by fluctuating viscous
stresses. We express the drag magnetoresistivity in terms of the intrinsic
dissipative coefficients and basic thermodynamic properties of the electron
fluid. Our results are derived nonperturbatively in interaction strength and do
not rely on assuming Fermi-liquid behavior of the electron liquid, and
applicable also in the regimes of semiquantum and highly correlated classical
fluids.
