RESEARCH OBJECTIVES:
The research objectives at the the SPINLab are:
- to conduct fluid mechanics experiments relevant to the our understanding of large-scale flow processes occurring on and within planetary bodies throughout the solar system
- to carry out numerical studies that simulate processes not easily modeled in the Earth-bound laboratory and that complement our experimental simulations

CURRENT RESEARCH INTERESTS:
-Dynamics of Planetary Interiors
-Geophysical and planetary fluid dynamics
-Fluid mechanics of convection systems
-Zonal flow generation in planetary atmospheres
-Planetary magnetic field generation

Graduate student Eric King has led the development of an experimental rotating magnetoconvection device (RoMag). Experiments made in RoMag are providing detailed characterizations of flow dynamics at nearly planetary parameter values and produce quantitative measurements of the flow fields that are believed to be critical components of planetary dynamos. The quantitative results will test several long-held, but unproven, tenets regarding the dynamics of convection occurring in planetary cores. The RMCD utilizes the recently developed technique of acoustic Doppler velocimetry to study convection in liquid gallium, which has material properties similar to that of the iron-rich planetary core fluid. The Doppler system allows us to quantify convective velocities in a thermally driven (< 10^5 W/m^2), large volume (6.2 L), right cylindrical rotating magnetoconvection tank. This set-up has the advantage of attaining an Elsasser number, the ratio of magnetic and rotational forces, that is close to one, as is estimated for the geodynamo.

Quantitative velocity measurements in gallium are being used to test accepted theories about how the Elsasser number may control convection in the core. In addition to acoustic Doppler velocimetry, diagnostic measurements include thermometry and Hall probe magnetometry. Together these diagnostics provide a powerful, new platform for generating quantitative data relevant to the geodynamo and planetary core processes.

See more: RMCD Development Poster | ROMAG Movie | ROMAG Poster 1 | ROMAG Poster 2

Researchers have long assumed that Earth's core processes occur within a nearly perfect spherical shell and that this condition is sufficient to explain the geodetic and geomagnetic observations. However, seismological and mantle convection studies suggest that the core-mantle boundary (CMB) contains variations in shape and temperature, creating a heterogeneous boundary. Recent models suggest that boundary heterogeneities may control both the large-scale generation of the Earth's magnetic field and the exchange of angular momentum between the mantle and core. In fact, the effects of heterogeneous boundaries may be one of the most important controlling factors influencing Earth's core processes. However, we know of only a few laboratory experiments that have been conducted to study the effects of thermal heterogeneity and none that investigate the effects of topographic heterogeneity.

Graduate Student Mike Calkins is leading our project to measure the effects of heterogeneous boundary topography on core flows, using coupled laboratory and numerical experiments. While previous studies of topographic heterogeneity have utilized estimates inferred from seismic studies, the goal of our study is to determine the upper bounds of core-mantle topography for a given imposed core-style flow.

Significant scientific resources are presently being devoted to the study of planetary bodies that undergo librational motions. Yet no comprehensive studies to date have investigated how libration, the oscillatory motion of a planet around its rotation axis, affects interior planetary fluid dynamics. To begin looking at the effects of libration, Jerome Noir is carrying out experimental and numerical simulations (in collaboration with Johannes Wicht of the Max Plank Institute) of librationally-driven core flow. Our goals are to produce detailed models of libration driven flows within planetary cores and briny subsurface oceans. Understanding these flows should enable us to predict mechanical coupling coefficients and induced planetary magnetic fields. Thereby, we hope to develop an essential tool for inferring interior planetary structure and dynamics using observations of planetary librations and magnetic fields. Such a tool will prove relevant to a number of planetary bodies including Mercury, Europa, Io, Callisto, Ganymede and the Earth's Moon. In particular, this approach will have immediate application, as detailed models of Mercury's libration-driven core flow will help interpret libration and magnetic field measurements provided by NASA's MESSENGER Spacecraft.

Boundary layer instabilities driven by librational forcing.
	Jerome Noir discussing the libration experiment with Michael Burin.

In collaboration with Moritz Heimpel (University of Alberta, Edmonton, Canada), Lorraine Allen (US Coast Guard Academy) and Johannes Wicht (Max Plank Institute for Solar System Research, Katlenburg-Lindau, Germany), SPINLab members Krista Soderlund, Eric King and Prof. Aurnou have been carrying out numerical studies of zonal wind generation on the giant planets. Our simulations suggest that convection in the nearly adiabatic deep atmospheres of the Jupiter and Saturn will tend to produce nearly two-dimensional turbulence that naturally generates a flow pattern with a strong eastward equatorial jet and multiple jets at higher latitudes. Further simulations suggest that on Uranus and Neptune the convective turbulence may more three-dimensional than on Jupiter or Saturn.

a) Giant planets model results; b) Ice Giant model results. (Image: K. Soderlund.)