Iron snow zones as a mechanism for generating Mercury's weak observed magnetic field

摘要

The anomalously weak observed magnetic field of Mercury is difficult to explain by appealing to crustal remanent magnetism or Earth-like dynamo mechanisms. Although the field is likely caused by a hydromagnetic dynamo, the field strength is far weaker than the characteristic strength expected from an active, strong field dynamo. Recent experimental work has shown that sources of compositional convection exist in mixtures of sulfur and iron at temperatures and pressures relevant to Mercury's core. The number and location of these iron "snow" zones is dependent on the sulfur content of the liquid portion of the core. We use a numerical dynamo model to show that the core states which include a snow zone midway through the core produce the observed field strength and expected field partitioning of the Mercurian magnetic field.