Possible Approach to Detect Mysterious Saturnian Convective Dynamo via its Gravitational Field----中国科学院紫金山天文台

Seminar Title	Possible Approach to Detect Mysterious Saturnian Convective Dynamo via its Gravitational Field

Speaker:	Prof. KONG Dali

Affiliation:	(SHAO)

When	Wednesday morning, Sept. 4, 10:30 a.m.

Where:	Room 302 No.3 building , Xianlin campus (PMO, CAS)
	Welcome to Attend

	( PMO Academic Committee & Academic Circulating committee)

Abstract: The Cassini Grand Finale Mission has carried out unprecedentedly accurate measurements of Saturnian gravity and magnetic fields. Both measurements are crucial for understanding internal state of Saturn. However, interpretations of the measurements have been subject to uncertainties because of tremendous difficulties in self-consistent and reliable forward modeling of interior structure, zonal flows and convective dynamo, which are essentially inter-coupled interior physics. Based on the latest inferences of interior structure, a 3D self-consistent finite-element modeling of convective dynamo flows is adopted to compute possible gravitational signals related to deep dynamo dynamics of Saturn. It has long been expected that successful detections of such signals can tell a serial of important but by far unknown features of Saturnian dynamo, which can further help constrain interior structure, gaseous equation of state and existence of deep zonal flows in molecular hydrogen envelop. It is concluded in this work that the gravity determination done by Cassini Grand Finale mission is insufficient for distinguishing between 'weak-field dynamo' and 'strong-field dynamo' scenarios. We also propose, for future Saturn missions, a few orbit configurations that are able to serve this purpose, although engineering implementations of them could be challenging. Unlike previous missions, we have designed a series of orbits and carried out simulation experiments to theoretically verify the feasibility of detecting convective dynamo using gravity field information. The inclination angle of a satellite orbit, combined with altitude, significantly affects the orbit structure, and especially the orbit sensitiveness on capturing the gravity signal. From our results, we find that a middle inclination angle orbit with orbital height 1000 km and three-month tracking could help solve the aimed gravitational coefficients resulting from distortions associated with deep convective dynamo of Saturn.

Short Bio of the Speaker:

Dr. Dali Kong obtained his BSc degree from Department of Astronomy, Nanjing University in 2008. He then spent time in University of Exeter, UK and earned the PhD degree in planetary fluid dynamics in 2012. After that, Dr. Kong carried on with his research fellowship in the Centre for Geophysical and Astrophysical Fluid Dynamics, University of Exeter. In 2017, Dr. Kong took up a position of research scientist and relocated to Shanghai Astronomical Observatory, Chinese Academy of Sciences. By October 2018, Dr. Kong has authored 42 peer-reviewed publications. He was awarded the 2016 Royal Astronomical Society Winton Capital Prize (G) for his contribution in studies of gaseous planets.