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Akira Hasegawa | |
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長谷川晃 | |
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| Born | (1934-06-17)17 June 1934 Tokyo, Japan |
| Died | 22 June 2025(2025-06-22) (aged 91) |
| Education | University of Osaka (B.E., M.E.) University of California, Berkeley (Ph.D.) Nagoya University (Sc.D.) |
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| Scientific career | |
| Fields | Plasma physics,Optical solitons |
| Institutions | Bell Labs University of Osaka Nagoya University Columbia University École Polytechnique Fédérale de Lausanne |
| Thesis | Plasma Computer Simulation Using Sheet Current Model (1964) |
| Doctoral advisor | Charles K. Birdsall |
Akira Hasegawa (Japanese:長谷川 晃,Hepburn:Hasegawa Akira; 17 June 1934 – 22 June 2025) was a Japanese theoretical physicist and engineer who worked in the U.S. and Japan. He is known for his work in the derivation of theHasegawa–Mima equation,[1] which describes fundamentalplasma turbulence and the consequent generation of zonal flow that controlsplasma diffusion. Hasegawa also made the discovery ofoptical solitons[2] inglass fibers, a concept that is essential for high speedoptical communications.
Hasegawa was the first to suggest the existence ofoptical solitons in 1973. In 1974, he (together withLiu Chen) showed that plasmas could be heated with the kineticAlfvén wave.[3] Hasegawa and Chen introduced the concept of the kinetic Alfven wave to illustrate the microscopic process of theAlfven wave heating.[4] In 1977, Hasegawa introduced theHasegawa–Mima equation to describe turbulence inTokamak plasmas and then further developed it in the 1980s (with Masahiro Wakatani) to obtain the Hasegawa–Wakatani equation.[5] The equation predicted aninverse cascade in the turbulent energy spectrum (i.e., from small to large wavelengths) andzonal flows (in the azimuthal direction in the Tokamak) that can control radial turbulent diffusion.[6] With Wakatani, he wrote a paper on self-organized turbulence in plasmas.[7]
Hasegawa's proposal to trap plasmas with a dipole magnet similar to Earth's magnetic field, where turbulence caused by solar wind stabilizes the trap, was implemented in the first dipole plasma experiment[8] at University of Tokyo by Prof. Zensho Yoshida. In 2010, aplasma experiment with a floating dipole was also built at theMassachusetts Institute of Technology.[9]
Hasegawa was born on 17 June 1934, inTokyo Prefecture.[10] He was a graduate of the Department of Communications Engineering at theUniversity of Osaka, Japan and was aFulbright student at theUniversity of California, Berkeley, where he completed his Ph.D. under the supervision of Charles K. Birdsall in 1964. The title of his dissertation wasPlasma Computer Simulation Using Sheet Current Model.
He subsequently took a post doctoral position atBell Laboratories for six months, where he worked withSolomon J. Buchsbaum. Hasegawa was an associate professor in the Faculty of Engineering Science of the University of Osaka from 1964 to 1968. During this period, he served as a visiting professor at the Institute of Plasma Physics atNagoya University and received the Doctor of Science Degree from the Department of Physics at Nagoya University.
Hasegawa rejoined Bell Laboratories in 1968, where he stayed as a distinguished member of technical staff until 1991. During his time at Bell Laboratories, he also became an adjunct professor in the Department of Applied Physics atColumbia University from 1971. He was a Distinguished Visiting Professor at theÉcole Polytechnique Fédérale de Lausanne in 1980 as well as a visiting professor at the Institute of Laser Engineering at Osaka University. Hasegawa was elected as Chairman of the Division of Plasma Physics of theAmerican Physical Society in 1990, when he reported to the President the importance offusion research based on advanced fuels to avoid undesirable consequences ofdeuterium tritium fusion. In 1991, he resigned from Bell Laboratories and transferred to the Faculty of Engineering at Osaka University. He retired in 1998.
In addition to over 250 scientific papers and several text books, Hasegawa published a number of books on the subjects of Japanese andZen culture, which he learned from his spiritual teacher,Kobori Nanrei Sohaku of theDaitoku-ji temple. Following his retirement from Osaka University, he took a position as a lecturer atKobe Women's University to teach a course on Happiness for Japanese Women, upon request of the founder of the university, Mrs. Kaname Yukiyoshi. He also worked as a professor atHimeji Dokkyo University andKochi University of Technology and was a special consultant withNTT Japan andBTG International.
Akira Hasegawa was born to Japanese parents who were divorced when he was very young. He was primarily raised by his mother, Kaoru Takata, who was a graduate of Science and Mathematics Department inNara Women's University His mother was a strong influence in developing his interest in mathematics. Hasegawa played on a baseball team while atNagasaka Junior High School. At Itami High School he was a member of the Science Club. While at Osaka University, he also played trombone in a Dixieland Jazz Band, which he and his friend formed. He spent all of his scholarship money to purchase a large collection of jazz records, extending fromBix Beiderbecke toMiles Davis.
In March 1961, prior to moving to the United States, Hasegawa was married to Miyoko. Together, they have two sons, Tomohiro and Atsushi, and a daughter, Akiko. He played tennis but mostly enjoyed playing golf. Akira enjoyed being a member of theRotary Club of Kyoto-East and publishing books on various non-science themes including history, finance, and culture. He believed that Japan is a country established on a unique matriarchal culture during theJomon period, some ten thousands of years BC.
In addition to an extensive academic publication record and the editorship and authorship of numerous scientific research level text books,[11][12][13][14][15][16][17][18][19] Hasegawa was prolific in the publication of various aspects of culture and philosophy in the past few years, writing on diverse topics such as life and entropy, the economy and finance,Lao Tzu andConfucius, as well as Japanese culture and religion. Many of the texts are available electronically in Japanese, as well as in English and include such titles as: "A Story of Life and Health",[20] "A Story of Money",[21] "Fund Management for those near Retirement",[22] "Method of Investments for Private Pension",[23] "The One World of Lao Tzu and Modern Physics: A Dialogue with a Zen Abbot",[24] "Mai and Dance and Japanese Culture",[25] "Enjoying Wine",[26] "Science and Religion",[27] "How to Increase Productivity in Service Industries",[28] "Japanese Women Changing the World".[29]
Hasegawa died on 22 June 2025, at the age of 91.[30]
Hasegawa made a number of seminal contributions in the subject of waves and turbulence in plasmas as well as in information transfer inoptical fibers. While at Bell Labs as a post doc, he succeeded in the theoretical explanation of a unique resonant phenomenon in magnetized plasma, referred to as the Buchsbaum–Hasegawa resonance.[31] While at the Faculty of Engineering Science Osaka University, he pioneered a computer simulation of plasmas inmagnetic fields and supervised numerous students, including, Tetsuo Kamimura (Professor,Meijo University), Katsunobu Nishihara (Professor,Osaka University) and Hideo Okuda (Professor,Princeton University). Kiyoshi Yatsui (Professor,Nagaoka University of Technology) was an assistant in his group. During this period, he became acquainted with Professor Toshiya Taniuchi ofNagoya University. Professor Taniuchi then became a mentor of Hasegawa on nonlinear waves in plasmas and fluids.
In 1968, while at Bell Laboratories, Hasegawa joined a group in charge ofspace plasmas. His first theoretical work was to show that the observed oscillation on a satellite in the Earth'smagnetosphere can be explained by an excitation of mirror instability coupled with a drift wave mode and named it the drift mirror instability.[32] This has become a pioneering work in space plasma instabilities. In 1973, while he was working on studies of the nonlinear evolution ofWhistler wave envelope, he discovered the same equation, the nonlinearSchrödinger equation, applied to the envelope oflight pulses in glass fibers. With the help ofcomputer simulation undertaken in collaboration withFred Tappert, he demonstrated transmission of a stable nonlinear optical pulse in fiber, which was later to be known as the optical soliton.[2] The experimental verification of existence of the optical soliton was first made by L. F. Mollenauer et al of Bell Laboratories in 1980.[33] The nonlinear Schrödinger equation is now widely used for simulation of optical signal transfer in fibers over inter-continental distances[34] and not solely limited to solitons.
Hasegawa and Liu Chen succeeded in explaining the Earth's magnetic oscillation mechanism (now known as the Chen–Hasegawa resonance[35]) which was observed by his colleague,Louis J. Lanzerotti. This work also lead them to discover a new wave now called the kineticAlfvén wave[3] that resolved themagnetohydrodynamic singularity. A Bell Labs team ofCliff Surko (Professor atUniversity of California, San Diego) andRichart E. Slusher (Georgia Tech) discovered low frequency plasma turbulence by laser scattering in thePrinceton plasma machine. Hasegawa withKunioki Mima derived a two dimensional nonlinear wave equation that describes the observed turbulence spectra. This equation, now called theHasegawa–Mima equation,[1] is widely used as the fundamental equation to describe low frequency plasmaturbulence. One unique property of the equation is the existence of an inverse cascade of turbulent spectra which may formcoherent structures such as zonal flow in theazimuthal direction incylindrical plasmas.[6] Hasegawa with Masahiro Wakatani extended the equation to the realistic geometry of plasmas confined in atoroidal magnetic field (Hasegawa–Wakatani equation) and demonstrated the universal excitation of zonal flow[5] as the consequence of turbulence.[7] To meet the needs of the high pressure confinement for advanced fusion fuel such asdeuterium-helium-3, in 1987 Hasegawa proposed[36] a plasmaconfinement by adipole magnetic field generated by floatingsuperconducting ring current.Devices based on this idea were built atUniversity of Tokyo by a research group headed by Professor Z. Yoshida[8] and byMIT andColumbia University team led by Professors J. Kesner and M.E. Mauel,[9] and successful high pressure plasma confinements were demonstrated.
In September 1991, Hasegawa took a position of Professor of Communications Engineering in the Faculty of Engineering atOsaka University and started a new group ofoptical soliton based communication systems. He established international as well as domestic research groups that concentrated on ultra-high speed communications based on optical solitons. The group successfully demonstrated soliton based, all-optical ultra high speed communication over inter-continental distances. A student during this period, Toshihiko Hirooka now works as a professor atTohoku University.
After retirement, Hasegawa proposed two important concepts infusion devices. One is the idea that a fusion device operates as a power amplifier rather than as a reactor. Here, the device operates with the help of continuous injection of electromagnetic power that providesnegentropy which maintains the desirable plasma pressure profile. The other is the concept ofchiral asymmetry of vortices generated in plasma turbulence wherevortices having positive (negative) core charge tends to expand (to shrink) which is essential in the formation of proper zonal flow for plasma confinement.
Hasegawa was a Fellow of IEEE and theAmerican Physical Society.[37] Internationally, he was recognized as a recipient of the 1991 Rank Prize (British), 1995 Moet Hennessy, Louis Vuitton Da Vinci of Excellence Prize (French), 1999 IEEE/LEOS Quantum Electronics Award, and the 2000James Clerk Maxwell Prize for Plasma Physics of the American Physical Society.[38] In his citation, his innovative discoveries and fundamental contributions to the theory of turbulence of nonlineardrift waves, the spread ofAlfvén waves in the laboratory and in space plasma, as well asoptical solitons and their application intelecommunications were highlighted. He also shared with Kuniaki Mima and Pat Diamond the 2011 European Physical SocietyHannes Alfvén Prize.[39]
Domestically, Hasegawa received several awards including, the 1996 C&C Prize, 1996 Achievement Prize of the Institute of Electronics, Information and Communication Engineers (Japan), 1993 Shida Rinzaburo Prize (Japanese Ministry of Post and Telecommunications) and the 1995 Hattori (Seiko) Houkou Prize. He received the 2008Japan Academy Prize and in 2010 TheOrder of the Sacred Treasure, Gold Rays with Neck Ribbon from theJapanese Emperor.
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