Masaaki Yamada is a Distinguished Laboratory Research Fellow at Princeton Plasma Physics Laboratory (PPPL) and the Head of the Magnetic Reconnection Experiment (MRX) research program. He received his B.S. and M.S. from University of Tokyo and his Ph.D. in physics (1973) from University of Illinois. He is a pioneer of laboratory astrophysics, and his research interests extend from magnetic reconnection to micro-turbulence phenomena, magnetic fluctuations in plasmas, ion acoustic waves, beam-plasma instabilities, and spheromak dynamics.
Upon graduation from the University of Illinois, Masaaki Yamada moved to PPPL, and he became the head of the Q-1 research group (1977) and carried out a variety of basic plasma physics experiments including observations of current-driven turbulent ion heating and beam-driven lower hybrid and ion cyclotron instabilities. During 1978–1988, he headed spheromak research, utilizing the S-1 device, and conducted fundamental experiments supporting fusion energy and magnetized plasma dynamics. Together with Harold Furth, Tom Stix, and PPPL colleagues, Yamada (1980) proposed and demonstrated the inductive formation method for the spheromak configuration using the transfer of poloidal and toroidal magnetic flux from an inductive “flux-core.” This highly effective quasi-static spheromak formation scheme on S-1 enabled crucial early observations (1985) of Taylor relaxation, tilt instability, and magnetic compression.
The success of the S-1 experiment lead Yamada to propose and develop the laboratory configuration to investigate magnetic reconnection through the collision and merging of two spheromak plasmas. In collaboration with Yashusi Ono and colleagues at the University of Tokyo, Yamada made the first laboratory measurements (1990) of forced magnetic reconnection through the merging of two spheromaks. These experiments revealed the importance of a fully three-dimensional description of magnetic reconnection and showed how the global property of magnetic helicity dramatically influences the local rate of reconnection.
Following these experiments, Dr. Yamada designed and completed building a new reconnection experiment at Princeton (1995), the Magnetic Reconnection Experiment (MRX), to explore the fundamental physics of magnetic reconnection over a wide range of dynamical regimes. Yamada's observational ingenuity lead to quantitative studies of reconnection over a wide range of plasma collisionality and magnetic topology. MRX facilitated the first well-controlled and carefully diagnosed studies of the current sheet structure that Yamada reported at the 1996 Annual Meeting of the APS Division of Plasma Physics. Subsequent experiments confirmed the characteristics of the Sweet-Parker model for the rate of two-dimensional reconnection and observed the electromagnetic wave activity associated with the reconnection process. For these experiments, Yamada and colleagues, Hantao Ji, Scott Hsu, and Troy Carter were awarded the John Dawson Award for Excellence in Plasma Physics Award in 2002. In the following years, Yamada continued to lead the MRX group and to acquire additional observations and insights of magnetic reconnection. These included discovery of anomalous resistivity in the current sheet layer, the laboratory observation that the thickness of the current layer during fast reconnection is of the scale of the ion skin depth, the discovery of that strong magnetic fluctuations in the current sheet are related to anomalous resistivity, and first laboratory observation of the quadrupole magnetic field component perpendicular to the reconnection plane as evidence of MHD Hall effects which derives from two-fluid dynamics in the reconnection layer.
The citation for Dr. Yamada's 2015 James Clerk Maxwell Prize reads:
For fundamental experimental studies of magnetic reconnection relevant to space, astrophysical and fusion plasmas, and for pioneering contributions to the field of laboratory plasma astrophysics.
Dr. Masaaki Yamada is a Fellow of the APS. He has been an active organizer of the Interactive Plasma Experiments in Laboratory and Space (IPELS) biannual conferences and annual US-Japan workshops on magnetic reconnection that have gathered together the space physics and laboratory plasma physics communities and a co-leader of the multi-institutional Center for Magnetic Self-Organization. He has been the doctoral thesis advisor for a dozen graduate students of Princeton University, the University of Tokyo, and Purdue University. Dr. Yamada has held invited professor positions at École Polytechnique Fédérale de Lausanne, Switzerland (1988), Kyoto University, Japan (1989), and the University of Tokyo, Japan (1994 and 2010).
