by Academician Yevgeny VELIKHOV, President of the "Kurchatov Institute" Russian Research Center, Academician Vitaly SHAFRANOV, senior researcher of the Center

In 2003 it was 100th birthday of Acad. Mikhail Leontovich (1903 - 1981), the founder of two major schools of research-in radiophysics and plasma physics. Together with his colleagues and pupils he developed a field of science on what we call the fourth state of matter whose finest particles are not atoms and molecules, but "bare" (naked) atomic nuclei and electrons. Plasma of this kind consisting of two hydrogen isotopes-deuterium and tritium, and heated to temperatures higher than those in the bowels of the Sun has been produced after half a century of theoretical and experimental studies. It is obtained at powerful installations for controlled thermonuclear fusion and in a few years? time it should become the actuating medium (working substance) of an international thermonuclear reactor. It will be based on the tokamak toroidal magnetic system developed at the Kurchatov Institute of Atomic Energy (now "Kurchatov Institute" Research Center) which received international recognition in the early 1970s.

Back in 1946 the then President of the USSR Academy of Sciences, Acad. Sergey Vavilov, paid tribute to Mikhail Leontovich as "teacher of the young". One of the brightest facets of his personality was already plain to see even at that time and it was his truly parental attitude to the "beginners" in science. In his relations with them he was strikingly patient, sympathetic, tactful, and sensitive without being obtrusive, never urging anyone with his work. He took time to discuss with each of them the progress of his work and if there were problems, he would sit down together with his "charge" and spend hours in search of the solution of his problem. And this constant readiness of their leader to help gave his "pupils" added energy and inspiration.

His seminars are remembered by many. No matter who took the floor-a man of experience or a "youngster", Leontovich was "all ears" right from the start. With his eyes fixed on the blackboard covered with formulas, he seemed to be reassessing the central problem and the associated logic and conclusions. As often as not he would try to help out by suggesting a general solution while demonstrating erroneous conclusions of the author.

Mikhail Alexandrovich always took a benevolent attitude to the manifold research "inclinations" of his staff with his only concern being their "intellectual level". And it was not accidental that representatives of different fields of science, eminent scholars, members and corresponding members of the Academy, regard themselves his pupils. And that includes not only those who received from him some concrete help, but simply those who happened to be associated with him for even some short period of time, who happened to experience the remarkable atmosphere, or aura generated by Leontovich and his remarkable personality. This highly ethical general scientific and cultural atmosphere which surrounded him was

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instructive in many ways, served as a source of attraction, helping generate new ideas paving the way to new and promising areas of research.

One should note at this point that Leontovich never praised his pupils in person, with his kind words reaching them only through others. He often took the role of an umpire in scientific controversies and arguments of his associates, often taking them even closer to heart than the "wranglers" and urging them to write a common article and going out of his way to promote their reconciliation.

Acad. Leontovich was always ready to get to know the families of his junior colleagues, remembered many names and asking them about their health and work. And he was always ready to help. Being modest and unpretentious himself, he regarded domestic problems of his young associates as snags interfering with their work. Here is just one such example. Two young researchers (later members of the Academy) were promised new apartments. (In those years such problems were dealt with in our country by local trade unions.) When Leontovich learned that the applications of his "youngsters" were ignored, he lost his temper and tore down the list of applicants from the notice-board. This "hooligan" outbreak of the academician produced the due impression and justice was restored.

What Mikhail Leontovich expected from his younger colleagues was not only zeal for knowledge and research, but a truly honest attitude to work and life. He set an example of high ethics, intolerance to hypocrisy, time-serving, abuse of human dignity, arbitrariness and all kinds of injustice, especially that of what he called "unscientific" kind. And it would be no exaggeration to call him a pillar of morality of the academic community. Time and again he expressed his sound and principled opinions concerning new candidates for Academy membership. Having this kind of an "inspector" (and later his followers) helped keep up the professional level of our top academic community.

Mikhail Leontovich must have inherited his best personal qualities from his forefathers among whom there were prominent scholars, engineers and medics. His father, Alexander Vasilyevich, was a prominent physiologist (from 1929 member of the Ukrainian Academy). In 1913 he was expelled from Kiev University for supporting the revolutionaries. But being a leading specialist, he was put in charge of the Chair of Physiology at the Petrovsko-Razumovsky Agricultural Institute (now the Timiryazev Agricultural Aca-

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demy) and moved to Moscow which was less conservative than Kiev.

There Mikhail entered a gymnasium and took special interest in chemistry and geology. Leontovich the senior focused on mathematical statistics and even wrote a textbook on the theory of probability (used by one of the authors of the present article). This new "zeal" was passed from the father to the son and while at the sixth grade in school (today-ninth grade) he mastered the beginnings of higher mathematics without any outside help. Feeling quite at ease with this subject he became a student of the Department of Physics and Mathematics of Moscow State University in 1919.

In that difficult "hungry" year for our country his mother, Vera Viktorovna, an oculist, died of mielitis. His father married again and Mikhail decided to live separately and take care of his younger sister Yevgenia. Being in need of money, he got a job, without leaving the university, at the Institute of Biological Physics (laboratory of the Kursk Magnetic Anomaly). It was headed by Acad. Pyotr Lazarev. At his new place of work he became acquainted with some prominent scientists and engineers and later recalled this period of his life with a special feeling.

Among his friends at the University were future Members of the Academy- A. Andronov (1946), P. Novikov (1960) and Corresponding Member N. Pariysky (1968). Leontovich was "moulded" as a scientist very early in life. From 1925 he and Alexander Andronov (who married his sister Yevgenia), who later became the founder of the school of theory of non-linear oscillations, continued their education at the postgraduate course of Moscow State University under the guidance of Acad. L. Mandelstam, a brilliant physicist, who was in charge of the Chair of Thermal Physics. During the following year the young researchers developed what they called a general quantitative theory of molecular scattering of light by liquid surface with random variations, small in comparison with the length of a light wave. Later on Acad. Leontovich himself verified the field of application of this theory experimentally. In 1928 L. Mandelstam and G. Landsberg (academician from 1946) discovered the phenomenon of combination light scatter in solid body, and Leontovich, working together with Landsberg, conducted additional studies of the phenomenon. During the three years of his postgraduate studies he published a total of 14 articles on optics in the prominent German journal Zeitschrift fur Physik . 1928 saw the publication of his pioneering work (as a co-author with L. Mandelstam) on what is called the tunnel effect - the passage of a potential barrier by a microparticle whose energy

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is below its height. This was followed by a number of his publications on the theory of sound absorption in gases and liquids.

After the post-graduate course Leontovich lectured at the Department of Physics and Mathematics of the Moscow University and in 1931 he helped Prof. S. Vavilov, future Academician and President of the USSR Academy of Sciences, to organize a practical course on optics. As remembered by his former students, the young lecturer spared no time helping them with experimental work and was always ready to help them.

In 1934 Mikhail Alexandrovich joined the Physics Institute of the USSR Academy (FIAN) and soon became one of its leading researchers. Acad. Igor Tamm (1953), who also became Nobel Prize laureate (1958) had this to say about Leontovich on the occasion of his award in 1935 of a Degree of Doctor of Physics and Mathematics: "Being distinguished by his extreme clarity of mind and critical depth of physical thought, rare manifold erudition and being in perfect command of the mathematical apparatus, he offers at the same time a rare example of a physicist who combines the gifts of a theorist and experimenter... A number of his works belong to such different fields as theory of oscillations, quantum theory and theory of relativity. But of the greatest importance are his works on optics and statistical physics... In this area he attained very important results which put him on a par with the biggest specialists in that field."

In his professional reference signed by Acad. Vavilov on the occasion of his nomination for the title of a Corresponding Member of the Academy in 1939, Acad. Vavilov stressed his particular qualities as a pedagogue: "A very large number of research works is carried out by post-graduates of Moscow State University and FIAN under the guidance of M. Leontovich. He is one of the leading figures of FIAN, and all of its staff, from junior ones to corresponding members of the Academy avail themselves of his assistance and consultations. Typical of Leontovich is a demanding approach to the quality of research work in general and his own studies in particular. His teaching work stands at the same high level as his scientific research. His books on statistical physics and physical optics enjoy tremendous popularity among students. The attendance of his lectures even now, when the choice is up to the students themselves, remains at one hundred percent."

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Acad. Leontovich made significant contributions to this country's defense during the Great Patriotic War with Nazi Germany. He took part in the development of a radio- navigational system of blind bombing and in radar studies for which he was decorated with the Popov Gold Medal.

During the same years Acad. Leontovich launched a cycle of fundamental studies on electrodynamics. Incidentally, it was back in 1938 that he formulated what are known as approximate border conditions for electromagnetic waves on the surface of objects with good conductance. These results were published only in 1948. The scientist combined his studies with his teaching work which had been started before the war: until 1946 he lectured at the Moscow State University and later on, until 1954 - at the Moscow Engineering Physical Institute.

His election as Active Member of the USSR Academy of Sciences in 1946 is connected with one unforgettable episode. Having learned on the eve of the elections from a Pravda article of President S. Vavilov that Prof. Igor Tamm was not on the list of the candidates he decided that he himself was somehow in the way of his friend whom he highly respected. So he wrote a letter of resignation to the Academy Presidium and when it was turned down, started asking the academicians to cast their ballots not for himself but for Tamm. But as fate would have it, it was Leontovich who received the top academic honor that year and Igor Tamm followed him only seven years later.

1951 marked the start of a new stage in the scientific efforts of Mikhail Leontovich. He was put in charge of theoretical studies on controlled thermonuclear fusion. The thing that attracted him most in that field was investigating the possibility of using thermonuclear reactions for electricity generation.

The following studies demonstrated the scale and complexity of that problem. In the search of its solutions Acad. Leontovich relied on his profound knowledge of electrodynamics and mathematical methods. His works on the assessment of electrodynamic forces generated by a shift of the current channel relative to the conductor sheath, on dynamics of a compression discharge and stabilizing effect of a strong linear magnetic field provided the basis for further progress in this field. When they were declassified, these studies received international recognition.

In the early 1960s it became obvious that the school of high-temperature plasma studies founded by Acad. Leontovich was the leading one. His associates and pupils formulated the basis of the theory of its turbulent state.

Later on researchers working on Russian-made tokamak T-3 obtained results which had been regarded as inaccessible before-plasma temperature of some 10 mln C ^o . Shortly after nearly all of the leading labs working on controlled thermonuclear fusion set their sights at tokamaks and much of the credit for that belongs to our theoreticians headed by Acad. Leontovich ^* .

But his school is more than a new big step forward to the horizons of science. He brought up a whole number of his dedicated students and followers who remain dedicated to his principles and objectives.

He is remembered as a person with penetrating eyes-simple in communication who appeared to know the answer to any question, but was void of any vanity. With his mind focused on matters of science, he had a fine sense of humor and never lost interest in the things around him. He never put up with meanness and remained kind and sincere with honest people around. This is how we shall remember him as long as we live.

^* See: V. Glukhikh et al., "On the Brink of Thermonuclear Era", Science in Russia, No. 3, 2003. - Ed .

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