Asteroid Magnetization from the Early Solar WindOPEN ACCESS 

Atma Anand, Jonathan Carroll-Nellenback, Eric G. Blackman, John A. Tarduno

submitted to MNRAS


“Magnetic fields provide an important probe of the thermal, material, and structural history of planetary and sub-planetary bodies. Core dynamos are a potential source of magnetic field amplification in differentiated bodies, but evidence of magnetization in undifferentiated bodies requires a different mechanism. Here we study stellar wind-induced magnetization (WIM) of an initially unmagnetized body using analytic theory and numerical simulations, employing the resistive MHD AstroBEAR adaptive mesh refinement (AMR) multiphysics code. We obtain a broadly applicable scaling relation for the peak magnetization achieved once a wind advects, piles-up, and drapes a body with magnetic field, reaching a quasi-steady state. We find that the dayside magnetic field for a sufficiently conductive body saturates when it balances the sum of incoming solar wind ram, magnetic, and thermal pressures. Stronger amplification results from pileup by denser and faster winds. Careful quantification of numerical diffusivity is required for accurately interpreting the peak magnetic field strength from simulations and corroborating with theory. As specifically applied to the Solar System, we find that early solar wind-induced magnetization is a viable explanation for observed paleointensities in some undifferentiated bodies. This magnetism mechanism may also be applicable for other Solar System bodies, including metal-rich bodies to be visited in future space missions such as the asteroid (16) Psyche. “