The effect of magnetic fields on double-diffusive fingering in astrophysics

Double-diffusive convection at high Prandtl number (Pr ~ O(1) or larger) has been well studied in geophysical contexts, but detailed investigations of the low Prandtl number regimes (Pr << 1) which are relevant to most astrophysical scenarios like stellar or planetary interiors have only recently become feasible. Since most low-Pr fluids in astrophysical scenarios are electrically conducting, it is possible that magnetic fields play a role in either enhancing or suppressing double-diffusive fingering convection, but to date there have been no investigations of such possibilities. Here we study the effects of both vertical (aligned with the gravitational axis) and horizontal background magnetic fields on the linear stability and nonlinear saturation of double-diffusive fingering convection, through a combination of theoretical work and direct numerical simulation (DNS). The possibility of dynamo behavior in the case where the fluid is also rotating is discussed, as well as the potential for magnetic effects to explain discrepancies between theoretical and observed mixing rates in low-mass red giant branch (RGB) stars.