Development of a roughened inner sphere for the three-meter model of the Earth's core

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Our planet's magnetic field directly affects near-Earth radiation during solar storms. This makes it important to understand the process that generates the magnetic field, and also to develop our capacity to predict its changes. This Division of Earth Science Instrumentation and Facilities Program award supports a project which aims to better understand the origin and changes of the Earth's magnetic field. Since these ongoing changes are a result of processes deep in the planet's outer core, it is difficult to do direct studies. The investigators have developed an NSF funded laboratory model of the Earth's outer core: the three-meter liquid sodium experiment. This project will involve a major design modification to the sodium experiment that is needed in order to better mimic the Earth's core, produce model magnetic fields, and enhance our ability to predict magnetic field changes. The project also serves to encourage public appreciation and understanding of geomagnetism through TV and web based documentaries, as well as videos posted on the research group's YouTube channel (www.youtube.com/user/n3umh); to open efforts and activities to non-scientists through frequent tours of the laboratory to a broad range of audiences; and to educate a new generation of scholars in geophysics experiments, including undergraduate mentoring and graduate student training.The Earth's main magnetic field is central to making our planet a habitable home. During solar maximum, solar storms produce deadly charged particle radiation. The geodynamo magnetic field, along with the Earth's atmosphere, serves to shield us from the worst of these. Nonetheless, solar storms can affect radio communications, the power grid, and spacecraft operations. Thus, we are motivated to understand the origins of the Earth's magnetic field, explore its dynamics, and potentially forecast its behavior. While we know the field changes dramatically over time, including through erratic reversals, there is no reliable predictive science for the weather occurring in the core and no full understanding of the Earth's dynamo generation. An NSF-funded three-meter (3-m) laboratory model of the Earth's core produces induced magnetic fields from rotating turbulence, modeling the dynamics of the Earth's core, and can be used for testing dynamo magnetic field forecasting. One second of experiments mimic approximately 5,000 years of core turbulence (based on the relative magnetic dipole diffusion time scales), allowing observations of detailed magnetic field evolution not possible for the Earth. While previous experiments have yielded important results in hydrodynamics and magnetohydrodynamics since operations began in 2008, the 3-m experiment now requires significant design modifications to increase magnetic field gain. This will be critical for continued studies, including those that directly address questions related to dynamo generation and sustenance. This project will undertake a major modification of the 3-m liquid sodium system that will allow attempting dynamo magnetic field action, and open the parameter space of the system to expand the potential of magnetohydrodynamics experiments. The project also makes direct contributions to the public appreciation and understanding of geomagnetism through TV and web based documentaries and frequent facility tours.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.