NEWS | Sept. 7, 2011

Sigma XI Honors Dr. Yi-Ming Wang with Pure Science Award

By Donna McKinney

Dr. Yi-Ming Wang, an astrophysicist at the Naval Research Laboratory, has been honored with the 2011 Sigma Xi Award for Pure Science presented by NRL's Edison Chapter of Sigma Xi. Wang is recognized for fundamental contributions on the nature of solar magnetic fields, the solar wind, and the sunspot cycle. The award was presented in a ceremony held on September 7, 2011.

Since joining NRL's Space Science Division in 1986, Wang has made a long series of innovative discoveries about the Sun's magnetic field and its outward extension into the heliosphere. He is recognized for discovering that the poleward meridional flow on the Sun's surface is part of a global circulation pattern that carries subsurface flux toward the equator of the Sun. This flow is now a critical component of flux-transport dynamos, and Wang's research is widely recognized as having led to that new field of study.

In addition, he showed that the outward expansion of the Sun's magnetic field is quantitatively related to the speed of the solar wind. This result formed the basis of the Wang-Sheeley-Arge model, which is now used routinely by the National Oceanic and Atmospheric Administration for space weather prediction. Wang was also able to solve a long-standing mystery concerning the behavior of coronal holes, the dark regions that are the sources of the solar wind; with his NRL colleague Dr. Neil Sheeley, he showed that the open magnetic fields in coronal holes are not tied to the differentially rotating photosphere, but continually reconnect with the surrounding closed fields so as to maintain a nearly rigid rotation. As part of his study of the Sun's meridional circulation, Wang recognized that the circulation speed could not be constant in time: in order to continue to reverse the polar fields over many cycles, the poleward surface flow must be faster during big sunspot cycles. This idea enabled him, in collaboration with NRL's Dr. Judith Lean and Sheeley, to model the variation of the Sun's magnetic field and total radiative output over the last 300 years; this model is now widely used in Sun-climate research.

Wang received his bachelor's degree in astronomy from Harvard College in 1971 and his doctorate in physics from Massachusetts Institute of Technology in 1976. He worked at the Astronomy Centre at the University of Sussex and the Astronomische Institute at the University of Bonn, specializing in high-energy astrophysics, before coming to the Naval Research Laboratory in 1986.

Wang served as an Associate Editor of the Journal of Geophysical Research - Space Physics from 2001 to 2004. He is a member of the American Astronomical Society and the International Astronomical Union. He has published 160 articles in refereed journals.