This research seeks to understand the Earth's magnetic field by using unique rotating liquid sodium experiments as models of the Earth's core. The Earth's magnetic field acts as a shield to radiation from the sun. It is dynamic and has been in decline for the past several hundred years. Since we do not understand how a turbulent flow in the core can generate magnetic fields, we presently cannot predict the future of the Earth's field. Experiments give a unique window by being laboratory models of the Earth's core.
These experiments match as many of the conditions as possible in the laboratory, including the importance of rotation, liquid metal induction, and significant magnetic forces. The experiments explore the flow dynamics and conditions by probing the motion and induced magnetic fields of the experiments. Broader impacts for this research include the key role that young researchers play in the ongoing projects. The mentoring of student researchers is a very important part of this project. As well, we have played, and hope to continue to play, an active role in science documentaries addressing changes in the geomagnetic field. The scientific results of this research have implications in geophysics, astrophysics, plasma physics, nonlinear dynamics, and fluid dynamics -- the research is inherently cross-disciplinary.
Intellectual Merit This NSF funded project at the University of Maryland wors to better understand the origin of the Earth's magnetic field. We do that using rapidly rotating turbulent flows in laboratory devices. The primary research outcomes from this project include documenting the presence of Coriolis restored waves in two devices one two foot in diameter (60 cm model), and one ten feed in diameter (thee meter model). We found that in the two foot diameter liquid sodium experiment the waves cause induced magnetic fields. These same waves have now been observed in the three meter system in water shear flows. As part of this project the three meter system became scientifically operational in water, with all systems fully operational. The experience we gained while running with water are valuable toward the sodium future experiments. The sodium has now arrived and the three meter system has been filled. In addition to the observations and characterization of inertial waves (Coriolis restored waves), we have also discovered precessionally driven waves in the three meter system. While the system is rotating at a steady rate, with inner and outer boundaries locked together, the earth's rotation drives flows. Essentially, the fluid cannot be in solid body rotation with both the container and the earth simultaneously. These precessionally driven flows may also occur in the Earth's outer core, driven by the 25,800 year precession of the Earth's rotation axis. Our observations of rapidly rotating turbulent flows are significant to our understanding of the flows in the Earth's core, as we cannot directly observe the fine structure of the core flows from surface or satellite measurements. The turbulent boundary layers and wave modes we characterize and observe should exist in the core and have direct effects on the Earth's magnetic field strength and dynamics. Broader Impacts An important part of this NSF funded project is the mentoring and training of a new generation of earth scientists. Undergraduate, graduate and post-doctoral young researchers participate in the ongoing experimental activity. In addition, significant public outreach toward an awareness of science was achieved through our youtube channel (n3umh) and the numerous documentaries filmed in the lab, including ones from the National Geographic Channel, the Science channel, and BBC4. Hundreds of laboratory tours were conducted during the term of this project of groups ranging from interested public lay-scientists, faculty from other universities and other countries, to undergraduate groups, and middle school groups (see attached image).
