The turbulent dynamo process is the generation of a magnetic field from the turbulent flow of a conducting fluid; which occurs for example in the Earth's core. An understanding of how turbulent flow structures generate the magnetic field is a central challenge in dynamo research. However, only one experiment has been able to produce a turbulent dynamo because of the extreme material properties and scale required; even in that case the fluid flows that generate the magnetic field have not yet been measured, and the fluid flows cannot be directly simulated in the strongly turbulent regime. The goals of this research plan are to use materials design to develop a revolutionary approach to magnetohydrodynamic experiments, and combine experiments and low-dimensional modeling to understand how fluid flow structures interact to generate magnetic fields in dynamos. The extreme parameter regime required for generating a turbulent dynamo in the laboratory will be reached by designing materials consisting of magnetic particles suspended in a liquid metal, i.e. micron-sized iron particles suspended in liquid gallium and its alloys. Such a fluid will have a high enough conductivity and magnetic susceptibility to build the universe's smallest turbulent dynamo (10 cm). The first simultaneous measurements of fluid flow and magnetic field in a turbulent dynamo will be made to connect their dynamics with an array of temperature and magnetic field probes at several locations around the apparatus. Turbulent flow structures can be reconstructed from such measurements, and modeled with low-dimensional models consisting of stochastic ordinary differential equations. These experimental and modeling techniques will be combined to understand how turbulent flow structures interact to produce magnetic fields.
Intellectual merit: This materials design is a novel approach to dynamos that would transform the field by opening up experimental research to more laboratories -- experiments could be scaled down and the need for large facilities to handle liquid sodium in traditional dynamo experiments would be eliminated. The tunable material properties of suspensions will allow for a direct comparison with simulations in the same parameter regime which has not been possible with traditional dynamo experiments. The first simultaneous measurements of turbulent flow structures and magnetic fields in an experimental dynamo will allow development and testing of models for how turbulent flow structures generate a magnetic field. The low-dimensional modeling techniques have the potential to become a new paradigm for simple understanding and quantitative predictions of different dynamical behaviors of large-scale structures in a wide variety of turbulent flows.
Broader impacts: Materials design will result in the development and characterization of fluids with useful tunable properties including high conductivity and a strong magnetic response; possible applications include magnetorheological brakes with reduced heat dissipation, and fluid power transformers with no moving solid parts. Astronomical dynamos such as the Earth and Sun have complicated dynamics that are not well-understood. Solar flares can interfere with long-wave radio communications and produce radiation hazards to spacecraft. Earth's magnetic field protects against dangerous radiation from the Sun. Modeling of magnetic dynamos may lead to better understanding of their dynamical behavior, which could have a positive impact on aerospace engineering. An integrated scientific research education program for undergraduates will be developed at UC Merced, a minority-serving research institution. This includes coordination of the lower division and upper division laboratory courses, and senior theses, with a focus on the scientific method and data analysis. These educational components will be evaluated according to a rubric for laboratory reports, theses, and presentations in line the physics program's learning objectives.
