Remembering Tom Chang

Tien Sun Chang (February 28, 1931 - January 20, 2024)
Tien Sun Chang, a formidable figure in the field of space physics who made significant contributions to our understanding of space plasma complexity, died January 20, 2024, in Troy, NY. He was 92.
For over three decades, Dr. Chang, also known as "Tom," was a leading figure at the Massachusetts Institute of Technology, where he directed the activities of theoretical geocosmo plasma physics. He established theCenter for Theoretical Geo/Cosmo Plasma Physics at MIT as founding director. During his tenure as director, he organized national and international conferences including the well-known Cambridge Workshop series in Theoretical Geo/Cosmo Plasma Physics and the Chapman Conference on Micro/Meso Scale Phenomena in Space Plasmas. His pioneering research was critical in advancing our understanding of complex phenomena related to plasma processes in various space environments, including the solar corona and Earth’s magnetosphere.
Among his many notable contributions was the theoretical work he did on the renormalization group, which led to his development of the rank order multifractal analysis method, known as ROMA. This innovative tool allowed for deeper insights into critical phenomena and has been widely adopted in space physics research.
Beyond his research, Dr. Chang was deeply committed to the academic community, serving as a senior visitor at the University of Cambridge, an Honorary Research Fellow at Harvard University’s Lyman Laboratory, a visiting lecturer at the Oak Ridge National Laboratory, and a Senior Fellow of the American Physical Society. He was the President of the Society of Engineering Science, a member of the NASA Space Physics Theory Working Group (SPTWG), and served as a member of the program committee of the Plasma Physics Division of the American Physical Society and the Committee for Visitors for the NSF Magnetospheric Physics Program. He held significant editorial roles, contributing to several important publications in his field including as the editor of the international journal Plasma Physics. He authored or edited more than 120 scientific publications, including 12 books and proceedings volumes. He continued to publish into his 80s. His last paper, “Beyond the Isotropic Lifshitz Endpoint,” was published in the Journal of Physics Communications in November 2019.
Born on February 28, 1931, in Mukden, China, to Hai-Ping Chang, a renowned civil engineer within the Nationalist government, and Cherry Kwan. During his childhood, Dr. Chang witnessed the upheaval of the Japanese invasion of China in World War II and the Communist revolution, during which his family fled for Taiwan. These early experiences forged a resilience that would characterize both his personal and professional life.
He received a Ph.D. in civil engineering from the University of Illinois at Urbana-Champaign in 1955, followed by a Ph.D. in physics from the University of Michigan at Ann-Arbor in 1963. His work early on also earned him the prestigious National Thompson Award from ASTM. His academic journey set the stage for a career that would span several prestigious institutions, starting as a young full professor at Virginia Polytechnic Institute, where he wrote his first book, Continuum Mechanics (Allyn and Bacon, 1965), co-authored with Daniel Frederick.
Dr. Chang also met his wife, Monica, while at Virginia Polytechnic Institute. She was a graduate student; he, a very young professor. Not long after their first encounter, she went to his living quarters to return a Scheaffer pen that he had lent to her. (At the time, ballpoint pens were expensive in Taiwan, where Monica grew up.) He must have been very happy to see her. Years later, he still remembered and told the children that anecdote. According to Monica, it was innocent, but told from his perspective, it was a veiled scheme to see him. The two never agreed on the motive but were happily married in 1961.
A few years later, they moved from Blacksburg, Virginia, to Raleigh, North Carolina, where Dr. Chang was a professor at N.C. State. In Raleigh, Monica gave birth to three children — Adele, Richard, and Alexandra — before the family moved to Lexington, Massachusetts, for his job at M.I.T., where Dr. Chang made his biggest mark.
At M.I.T., Dr. Chang was inspired and prolific, publishing papers across a wide range of topics, including wave-wave interactions involving lower hybrid waves, the polar wind, the solar wind, wave-particle resonant interactions, applications of the renormalization group, and complexity in space plasmas.
In 1991, Dr. Chang and his frequent collaborator, C.C. Wu, published a paper on the development of an innovative theory of complexity phenomena in space and astrophysical plasmas, using the concepts of self-organized criticality, topological phase transitions, and multifractal measures. In particular, they incorporated theoretical techniques using the dynamic renormalization group in the analytical calculations. They called the new method ROMA.
ROMA goes beyond the standard multifractal analysis and emerged from Dr. Chang's deep understanding and visionary view on critical phenomena. He always viewed turbulence as a critical phenomenon and this is perhaps one of the important parts of his legacy in physics.
Throughout his career, Dr. Chang was a high-demand lecturer and collaborator, and traveled extensively around the world, from Brussels to Hawai‘i to Singapore. Monica was a constant fixture by his side. No matter where they went, they indulged in Dr. Chang’s love for Chinese cuisine. They often joked that he could recommend a Chinese restaurant in pretty much every city capital in the world. He was also intent on passing down this love for travel to his children. He brought his family on summer vacations in Europe — taking trains from London to Italy and as far north at Sweden and Norway.
A driving enthusiast, he also piloted the family on regular road trips. There were weekend drives to the shopping outlets and lobster rolls in Kittery, Maine, and summer vacations to see family in Maryland and family friends in Raleigh. One ambitious summer, Dr. Chang drove from the Grand Canyon, through Las Vegas to Los Angeles and up the California coast to Big Sur and onward to San Francisco.
He also cherished his role as a grandfather, teaching his grandson, Oscar, to play chess and playing tag with his granddaughter, Emerson. During the Covid pandemic, he scheduled weekly video calls with both grandchildren to teach them about space and share his fascination with science and the endless possibilities of the Universe.
He was a man of many gifts. In college, Dr. Chang was an accomplished ballroom dancer and fencer, winning championships and trophies for both. He enjoyed playing chess, bridge and mahjong. Later in life, he designed and oversaw the renovation of the family home in Lexington, converting the midcentury Techbuilt structure into a contemporary masterpiece.
Dr. Chang continued to work and publish through his later years, demonstrating an unyielding dedication to his field. In 2015, Cambridge University Press published his book Introduction to Space Plasma Complexity, 50 years after his first. He was 86 years old. His papers are archived at the MIT Distinctive Collections.
In addition to his role as a loving and kind husband, father and grandfather, Dr. Chang leaves behind a legacy of intellectual curiosity and determination that continues to inspire the scientific community and all who knew him.