DISTINGUISHED LECTURE – PS
State Key Laboratory of Lunar and Planetary Sciences,
Macau University of Science and Technology
|Thu-02 Jul | 11:30 – 12:00|
|"The Location of the Saturnian Dynamo Revealed by the Cassini Grand Finale"|
Saturn possesses a strong and nearly axisymmetric magnetic field generated by a convection-driven dynamo in a deep metallic region via magnetohydrodynamic processes. However, the location of the dynamo region inside Saturn is unknown. The Cassini Grand Finale made unprecedented high-precision measurements of the gravitational field of Saturn that provide a new means of constraining the location of its dynamo. We have used both the equatorially symmetric and anti-symmetric components of the measured gravitational field to infer the location of the Saturnian dynamo. Our analysis reveals that the dynamo is primarily confined in a metallic region that is approximately 20,000 km below the surface of Saturn. The fast zonal flow of Saturn that produces measurable gravitational signatures is primarily confined within its 20,000 km thick outer molecular layer because the strong magnetic-braking effect in the dynamo region stops its deeper penetration.
Keke Zhang, a Fellow of AGU and RAS, obtained his BSc in Astronomy from the University of Nanjing, China, in 1982, his MSc in Geophysics and Space Physics from UCLA, USA, in 1985, and his PhD in Geophysics and Space Physics from UCLA, USA, in 1987. He is currently a professor in College of Engineering, Mathematics and Physical Sciences, University of Exeter, United Kingdom, and the director of State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau. His research areas include the theory and simulation of convection, instabilities and wave in rotating fluids, planetary magnetohydrodynamics, the shape, structure and gravity of giant gaseous planets, and planetary inverse problems. He is the author of nearly 200 publications in peer-reviewed scientific journals, including Nature, Science, PNAS, Physical Review Letters, Journal of Fluid Mechanics, Geophysical Research Letters, Journal of Geophysical Research, Earth and Planetary Science Letters, Proceedings of the Royal Society of London, Astrophysical Journal Letters, Icarus and SIAM Journal on Numerical Analysis, as well as articles in major review journals such as Annual Review of Fluid Mechanics and Annual Review of Earth and Planetary Sciences. He is also the Chief Scientist of Macau Science Satellites, the first low-latitude geomagnetic satellites focusing on the study of the South Atlantic Anomaly and the Earth's core dynamo, which are scheduled to be launched in 2021.