The Earth's magnetic field is dynamic and has been weakening for the last 160 years. The main field is generated in the Earth's core by the interaction of the rotating, turbulent liquid metal outer core and electrical currents induced by that motion. This project seeks to resolve how the rotation of the planet and turbulence affect the generation of magnetic fields in the Earth's core. At the heart of the project is the University of Maryland's three meter-diameter model of the Earth's core. That model uses 20 tons of rotating liquid metal and vessel to mimic the interaction of magnetic fields, turbulence and rotation in a scale model of the Earth's core. A magnetic sensor array is used to measure the dynamics of magnetic fields induced by the sodium flow. With this array the magnetic Gauss coefficients (spherical harmonic amplitudes) can be determined in order to understand the magnetic and hydrodynamic modes and their dynamics, study of the role of turbulent fluctuations in momentum transport and magnetic field generation, and resolve wave motions and their contribution to geophysical dynamical processes. These magnetic measurements are complimented by diagnostics rotating with the experiment, including torque sensors, ultrasound velocimetry, dynamic pressure probes, and dynamic wall velocity probes. This project includes the initial sodium operations for the three meter system, now that the device and preliminary water experiments are complete.
The project science, including the initial operation of a world unique device, is undertaken by a team of young researchers at the University of Maryland. The mentoring and career development experiences of the young scientists involved are an extremely important part of the project. Additionally, high-school science class field trips will be hosted to encourage the next generation of Science, Technology, Engineering, and Mathematics students from diverse backgrounds, while exposing them to an international science project. Finally, the measurements from the magnetic probe array allow the rendering of the magnetic fields into movies in order to convey our observations to the public.
The Earth's main magnetic field arises from the flow of liquid iron in the liquid outer core.The direction and strength of that field changes significantly on one to 100 year time scales. Indeed, the field strength has dropped 10% since scientists started measuring it some 170 years ago. We do not yet have a predictive science for that main field, so there are no tested tools for forcasting the future field strength. A main obsticle is the length and quality of magnetic field data we have, and the time scale for predictive tests -- ten to 100 years. We have built a three meter model of the earths core in order to understand the processes that lead a rotating turbulent flow of liquid metal to generate magnetic fields. That data can also be used toward the development of predictive tests; one second of the experimental data simulates 5000 years of planetary history. While the experimental model is an imperfect model of the earth's core (e.g. no radial inward gravity), it does produce high quality data of use in designing predictive tests, in an operating regeme similar to the Earth in terms of magnetic field gain. During this National Science Foundation grant period, we have performed the first liquid sodium tests in the three meter experiment. Findings include how the system amplifies magnetic fields in turbulent conditions, as well as the developmentof a new acoustic probe for measuring velocities, and the development of novel fire suppression techniques using cryogenic liquid nitrogen. The mentoring and training of a new generation of scientists is also a key component of this research, as well as public outreach through our web page, our lab youtube channel, and through participation in science documentaries. More information about our research can be found here: http://complex.umd.edu www.youtube.com/user/n3umh
