  The discovery of the intact metallic planetary core fragment orbiting the
white dwarf SDSS J1228+1040 within one Solar radius highlights the possibility
of detecting larger, unfragmented conducting cores around magnetic white dwarfs
through radio emission. Previous models of this decades-old idea focussed on
determining survivability of the cores based on their inward Lorentz drift
towards the star. However, gravitational tides may represent an equal or
dominant force. Here, we couple both effects by assuming a Maxwell rheological
model and performing simulations over the entire range of observable white
dwarf magnetic field strengths (10^3 -- 10^9 G) and their potential atmospheric
electrical conductivities (10^{-1} -- 10^4 S/m) in order to more accurately
constrain survivability lifetimes. This force coupling allows us to better
pinpoint the physical and orbital parameters which allow planetary cores to
survive for over a Gyr, maximizing the possibility that they can be detected.
The most robust survivors showcase high dynamic viscosities (>~ 10^{24} Pa*s)
and orbit within kG-level magnetic fields.

Earth and Planetary Astrophysics;Solar and Stellar Astrophysics