Chang-Yun (Charlie) Fan
January 7, 1918 - January 21, 2009
Dr.
Chang-Yun "Charlie" Fan, a Fellow of the American Physical Society,
who contributed significantly to diverse sub-fields of physics, died quietly
at home in Tucson, Arizona after 91 active years of health and happiness,
marred only by a final, brief battle with cancer. He will be remembered
for his charm and gentle good humor by a host of colleagues, former students
and friends, many of whom celebrated his long life and scientific achievements
in January 2008 with a symposium and banquet in his honor entitled "Fanfare!"
Born into a peasant family in Jiangsu Province, China in 1918, through
hard work, he gained entrance in 1936 to the National Central University
(NCU) in Nanjing, which, like many universities, was forced to move west
to escape the invading Japanese Army. Faculty, staff and students of NCU,
covering some stretches by foot, settled in Chongqing, the wartime capital,
where Charlie completed his BS in Physics in 1941. He stayed on in the
Physics Department as a teaching assistant for several years. Savings
enabled him to travel in 1947 to The University of Chicago, an institution
that attracted many Chinese physics students of his generation, which
included T. D. Lee and C. N. Yang. There he was awarded a PhD in Physics
in 1952 under Herbert I. Anderson for his work on beta-decay and internal
conversion (Phys. Rev. 87, 252, 1952). He began to contribute to the theory
of the origin of cosmic rays while still a doctoral student, and continued
in ensuing years (Phys. Rev. 79, 912, 1950 and 82, 211, 1951; Nuovo Cimento
Suppl. 10 (8), 457, 1958).
Fan pursued post-doctoral work from 1952 to 1957 as Research Associate
with Aden Meinel at the Yerkes Observatory of The University of Chicagos
Department of Astronomy and Astrophysics in Wisconsin. He built and utilized
the aurora gun to study the emission spectra of atmospheric
gases excited by both protons and electrons. His results provided a needed
understanding of auroral emission spectra. Meinel remembered him recently:
Charlie discovered the high degree of variability of the appearance
of H-alpha in the aurora, a puzzle that inspired similar research at the
Geophysical Institute in Fairbanks. Research toward explaining this behavior
is still active 45 years later, now using balloons and satellites, and
the answer still being debated. Charlie was the first to connect
this high degree of variability in the aurora to geomagnetic disturbances
(Astrophys. J., 128, 420, 1958).
In 1957, Fan accepted the position of Assistant Professor of Physics
at the University of Arkansas in Fayetteville, where he continued his
work on aurora, atomic physics and theories regarding the origin of cosmic
rays.
A year later, he returned to the University of Chicago to join the John
A. Simpson group as Senior Physicist and Research Associate Professor.
He remained at the Laboratory for Astrophysics and Space Research (LASR)
until 1967. The first decade of the Space Age was marked by Charlies
contributions (together with Peter Meyer and John Simpson) developing
space-borne cosmic-ray telescopes that used multiple solid-state detectors
in coincidence. This work contributed significantly to the discoveries
of the spatial separation of protons from electrons in radiation belts,
interplanetary shocks, elemental and isotopic composition of cosmic rays
and its modulation by the Sun, as well as the discovery of the anomalous
cosmic rays, which eventually led to our understanding of the interaction
between the solar wind and the local interstellar medium. Together with
George Gloeckler, Dieter Hovestadt and others, Charlie contributed to
the development of a new generation of charged-particle analyzers using
thin carbon foils and electrostatic analyzers, including the Low Energy
Charged Particle (LECP) instrument on Voyager 1 and 2 (Space Sci. Rev.,
21, 329, 1977). Space exploration with new instruments did not take Charlie
away from his love for atomic physics, as he measured the Lamb Shift in
6Li2+ (Phys. Rev. Lett., 15, 15, 1965).
In 1967, he joined the Physics Department of the University of Arizona,
where he served as Professor of Physics until his retirement in 1988.
During this period, while continuing his work in space physics, he expanded
his research in collaboration with other groups on campus; e.g.: measuring
Lamb Shift in 16O2+ with the Beam-Foil Group (Phys. Rev. Lett., 28, 1612,
1972); detecting cosmic-ray showers in Cerenkov light with the Smithsonian
Observatory (15th International Cosmic Ray Conference, Conference Papers
8, 233, 1977); and studying cosmic-ray variability and astrophysical events
using carbon dating with the Tree Ring Lab (16th International Cosmic
Ray Conference, Conference Papers 1, 106, 1979), to name a few.
Starting in 1972, Fan developed close collaborations with several groups
in China. Projects he initiated there include the study of cosmic rays
using carbon dating of tree rings at different latitudes (18th International
Cosmic Ray Conference, Conference Papers 3, 82, 1983), collection of cosmic
dust on NASAs Space Shuttles, and analysis of isotopic ratio of
6Li/7Li in lunar samples.
Charlies scientific career lives on in the work of the many former
students and younger collaborators who considered him their beloved teacher
and mentor. To his last day, Charlie invariably showed a genuine interest
in all people and always encouraged and challenged them to bring out their
best. A few days before he died, one of his oldest friends from the Yerkes
days visited him. He dismissed talk about himself with one quiet remark
and they talked science as usual. Charlie Fan approached both life and
death with a clear mind, dignity, humor, tolerance, curiosity, courage,
and a deep love for family and friends. He showed us how to live and showed
us how to die.
Davis Hartman, George Gloeckler, Neil Gehrels, Jacques LHeureux,
K. C. Hsieh
Submited to Physics Today to be published online.
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