Research Faculty: Sabine Stanley

Research

My research involves understanding planetary interior processes and evolution. Presently, my research focuses on studying planetary magnetic field generation. I use high performance computing to study the dynamo process (where convection in electrically conducting fluid regions inside planets generate self-sustaining magnetic fields). Investigating planetary magnetic fields can give us important information about the thermal history of a planet, its interior structure, and the fluid motions occuring in the core. Below I list some of my group's recent projects. For published papers, please see my CV.

Mars' paleomagnetic field as the result of a single-hemisphere dynamo

Stanley et al. (2008) Science

The only surface feature that Mars' crustal magnetic field correlates with is the hemispheric crustal dichotomy. Suggested formation mechanisms for the hemispheric crustal dichotomy include a giant low-angle impact or a degree-1 mantle circulation pattern. These formation mechanisms have implications for the temperature at Mars' CMB. We incorporated these temperature differences in a dynamo simulation and found that a single-hemisphere dynamo resulted, with strong fields generated only in the southern hemisphere. This may explain why Mars' crustal magnetic fields are only strong in the southern hemisphere: this is the only place where the active dynamo fields were strong!

Small Body Dynamos and the Angrite Parent Body

Angrites are ancient meteorites that provide us with information about the early solar system. Ben Weiss' lab at MIT has demonstrated that these meteorites have ancient remanent magnetic fields. This is the earliest known record of planetary magnetism. We have carried out theoretical analyses to determine that the Angrite Parent Body (most likely an asteroid-sized planetesimal) was capable of generating a dynamo for a few million years after the planetesimal's formation.

Weiss et al. (2008) Science

Saturn's axisymmetric magnetic field:

The near perfect axisymmetry of Saturn's observed magnetic field is problematic because of Cowling's Theorem. We used numerical models to determine if shearing flows in a thin stable layer surrounding Saturn's dynamo can explain the observed near perfect axisymmetry. We found that a necessary ingredient is thermal winds in the stable layer caused by temperature perturbations on the outer boundary of the layer. The only thermal winds that work are the ones produced by a warm equatorial region and cold polar regions. Luckily, this is the expected pattern in Saturn!

Stanley (2010) Geophys. Res. Lett.

Using reversed magnetic flux spots to determine inner core size:

We have determined that there is a correlation between the extent of intense reversed magnetic flux spots and the inner core size in numerical dynamo models. This gives future spacecraft missions a distinct feature to look for in magnetic field observations to determine a planet's inner core size.

Stanley et al. (2007) Geophys. Res. Lett.

Mercury's weak dipolar magnetic field:

We have shown that Mercury's weak observed magnetic field can be explained by a dynamo operating in a thin shell geometry where convection only occurs outside the tangent cylinder. We have also demonstrated that time varying small scale flux spots would be important to observe by the MESSENGER mission in order to determine the source of Mercury's field.
	Stanley et al. (2005) Earth Planet. Sci. Lett.

The non-dipolar, non-axisymmetric magnetic fields of Uranus and Neptune:

We have shown that the unusual magnetic fields of Uranus and Neptune can be explained by appealing to their convective region geometries. Numerical dynamos that operate in thin convecting shells surrounding a stably-stratified fluid interior produce magnetic fields very similar to those of Uranus and Neptune.

Stanley et al. (2004) Nature