Toshi Nishimura

Universit of California, Los Angeles

2016 James B. Macelwane Medal Winner

Toshi Nishimura was awarded the 2016 James B. Macelwane Medal at the AGU Fall Meeting Honors Ceremony, held on 14 December 2016 in San Francisco, Calif. The medal is for “significant contributions to the geophysical sciences by an outstanding ­­early-­career scientist.”


Yukitoshi “Toshi” Nishimura has transformed our understanding of plasma processes in ­­near-­Earth space. His research into substorms led the geospace research community to see this dynamic process as ­­system-­wide, wherein plasma is transported hundreds of thousands of kilometers from the dayside magnetopause to the magnetotail and then the inner magnetosphere, leading to an instability that creates beautiful auroras and changes Earth’s plasma environment. Using NASA Time History of Events and Macroscale Interactions during Substorms (­THEMIS) satellite plasma observations, together with images from ­­ground-­based auroral cameras, Toshi made the ­­first­ unequivocal causal connection between a space plasma process and a specific type of aurora. With that same research, Toshi also made the ­­first testable magnetic mapping between deep in the magnetosphere and the auroral ionosphere. I will limit my citation to the substorm work, but suffice it to say that I consider his auroral and mapping results to be equally important.

At the heart of Toshi’s research is innovative use of data from multiple observational platforms. He has combined plasma and wave observations from an international fleet of satellites with ­­ground-­based observations from auroral imagers, radars, and magnetometers to “see” geospace in fundamentally new ways. Where the rest of our field looked at the data from the perspective of the leading paradigms, Toshi found something new that did not fit existing ideas. What Toshi had found were north–south auroral forms stretching from the poleward to the equatorward edge of the auroral oval during, he argued, every substorm. This was perplexing, as neither dominant paradigm required anything that might correspond to these streamers.

Toshi faced a tough crowd not at all receptive to his ideas. He had to explain what the streamer signified in terms of magnetospheric dynamics, and so he did. He had to discover what the arrival of the streamer at the equatorward edge of the oval signified in terms of stability of the system, and so he did. Throughout, Toshi did the necessary work and injected his judicious creativity.

The influence of Toshi’s substorm research has been profound. Now substorm onset is seen as part of a larger process, where flux tubes move from the dayside, across the polar cap and the inner edge of the plasma sheet, carrying plasma with different physical properties that pushes a stable magnetotail into instability. Toshi brought ­­open-­mindedness and creativity to the problem and opened our eyes to a more comprehensive and ­­self-­consistent picture. In a very real sense, his work on the substorm has been paradigm shifting.

—Eric Donovan, University of Calgary, Calgary, Alb., Canada


Thank you, Eric, for your generous citation and nomination. I am truly grateful to the members of AGU for this honor, and I am humbled to join the company of the many prestigious scientists who have received the Macelwane Medal. This could not have happened without strong support and encouragement from my close colleagues, and I would like to take this opportunity to express my deep gratitude to them.

Unlike many of the past recipients in space physics and possibly in other fields, I did not build any instruments or large simulation codes by myself. My research almost always relies on hard work from my kind collaborators who invest a countless amount of time and effort making data available. My postdoctoral research at University of California, Los Angeles started when new science from NASA’s ­THEMIS mission led by Vassilis Angelopoulos was blooming. Eric Donovan and colleagues at University of Calgary and University of California, Berkeley built ­­world-­class imaging networks, and my postdoctoral advisor, Larry Lyons, shared with me his enthusiasm and ambition to solve the substorm problem. My part of the work was just to make things happen by cooking data. It was, of course, not easy, but I have been extremely fortunate to interact with the experts in the field who have paved the way for my research. I am also thankful to strong supporters in the community, particularly Bob Lysak.

Back when I worked in Japan, my advisors, Takayuki Ono and Takashi Kikuchi, as well as their lab members, opened the door for me to the exciting science of space physics. Their enthusiasm for science, deep knowledge, and dedication to education made me think that I wanted to be such a professional scientist. Sometimes they were a bit intense; we spent hours just to discuss a figure, and group meetings lasted until midnight. But all those became precious memories and still influence me.

I have also been privileged to work with talented students, most recently with Ying Zou, Bea ­­Gallardo-­Lacourt, Boyi Wang, and Cheng Zhen. I am grateful for their hard work, and it has been a great pleasure to witness their tremendous growth both academically and personally; I believe more is yet to come.

Finally, I wish to thank my family, in particular, my wife and fellow space physicist, Wen Li, for her kind support and sharing joy in life and science.

—Toshi Nishimura, University of California, Los Angeles