Gravitational-Electric Polarization as a Probe of Dark Matter and Modified Gravity

Abstract

Self-gravitating astrophysical plasmas naturally achieve a state of global electrical polarization, known as the Bally-Harrison effect, where an induced electric field counteracts the preferential thermal escape of electrons. In this work, we revisit the phenomenon of gravitational-electric polarization in astrophysical plasmas. By accounting for the dominant role of dark matter and comparing results across modified gravity frameworks, including MOND and MOG, we provide new constraints on the global charge-to-mass ratios of galaxies and clusters. We demonstrate that the effective charge-to-baryonic-mass ratio Q/M_bar is enhanced by a factor of 10 - 30 at the virial radii relative to purely baryonic predictions. By coupling gravitational polarization to galactic rotation, we derive a structurally linked seed field that reaches ~10^{-23} G in high-redshift proto-galaxies, sufficient for rapid dynamo saturation. We demonstrate that the distinct spatial signatures of these fields across different gravity theories provide a potential observational probe of the dark sector in the early universe. This enhancement may have significant implications in inferring properties of the intracluster medium and in determining the primordial seed magnetic field. The distinct radial and mass-dependent scaling laws predicted for each paradigm also provide a plausible diagnostic to distinguish between the presence of invisible mass and modifications to the gravitational law.