Martian magnetic field properties before the termination of its core dynamo

Abstract

Observed Martian crustal magnetism shows that the Mars does not possess a global-scale, dynamo-driven intrinsic magnetic field. In addition, the remnant field at the surface is hemi-spherically asymmetric. Our earlier simulation results suggest that the Martian dynamo could be sub-critical near its end (the energy required to sustain a subcritical dynamo is less than that to excite the dynamo) and the generated field morphology is non-dipolar. We further the study to examine the characteristics of the magnetic field via Empirical Orthogonal Function (EOF) analysis on the subcritical dynamo solutions with the Rayleigh number Rth = 2480 (below the critical point for the onset of the Martian dynamo). Our results show that the magnetic field is dominantly equatorial dipolar. Reversals and excursions occur frequently, and the magnetic dipole moment does not vary monotonically in time.