Στη μνήμη του Δασκάλου μου
In memory of my PhD Supervisor
One of the giants of space physics and 20th century astrophysics, Sir William Ian Axford, died on Saturday, March 13, 2010 at his Napier home in New Zealand after a long illness. Born in Dannevirke, N.Z., on January 2, 1933, he was 77 years old and widely regarded as one of New Zealand's greatest scientists. Despite his enduring passion for the New Zealand cricket and rugby teams, he lived most of his adult life outside New Zealand, starting in 1957 when he began his graduate studies in the Mathematics Department of Manchester University in the U.K. This occurred just prior to the launch of Sputnik I, an event that eventually greatly influenced his career. His thesis supervisor was the renowned aerodynamicist Sir James Lighthill, but Ian also learned a great deal from astrophysicists such as Franz Kahn and Allin Goldsworthy who were also at Manchester. Ian spent time at Cambridge's Department of Applied Mathematics and Theoretical Physics, encountering numerous interesting people who later distinguished themselves in plasma physics and astrophysics. Among them was Fred Hoyle whose ideas about cosmic rays very much later motivated one of Ian's most outstanding discoveries - the mechanism of diffusive shock acceleration - and with it the almost universally accepted explanation for the observed cosmic ray spectrum (at least up to about 10^14 eV/nucleon), solar energetic particle events, anomalous cosmic rays, and so forth. Ian's time in the U.K. cemented his style of scientific presentation, which, for some of us, occasionally presented a challenge - an interesting marriage of acute physical insight, an uncanny ability for order of magnitude estimates, and a desire that everything appear as effortless as possible! This conciseness of exposition made his publications both very readable on the surface, but very frustrating for students and others needing to work out the details.
From Cambridge, Axford joined the Defense Research Telecommunications Establishment (DRTE) In Ottawa, Canada where with Colin Hines, he did some of his most renowned work in developing our understanding of the Earth's magnetosphere and ionosphere (although Ian heartily disliked the distinction between the two preferring Gold's definition that incorporated both). Illustrating Ian's insight, one of his most renowned papers (with Colin Hines addressing magnetospheric convection) contains only one equation, E+VxB=0, despite being a theory paper! It was during this period too in Canada that Ian began to develop his lifelong appreciation for the science done in the then Soviet Union, often providing an important if informal role in communicating important observations and theoretical ideas to the west. This did not always endear Ian to some but he could be quite cutting in return. After a year spent in New Zealand, Ian moved to Cornell University in 1963. The `60's and the Apollo era was a time of considerable excitement for space physics - the golden age - with an abundance of funding, exciting open problems wherever one turned, and a community that was young and vigorous. Ian was at the forefront of many of the new ideas being developed, including ideas about cosmic ray transport, the effects of modulation (ranging from the cosmic ray transport equation, particle diffusion, the telegrapher equation, amongst others), solar flares, substorms, collisionless shocks, the always contentious issue of reconnection, and even the coronal heating problem. Indeed, the idea that the Earth possessed a bow shock was for a time extremely controversial given the absence of particle collisions but Ian was, with others, instrumental in developing and pushing forward the collisionless shock concept. While at Cornell and then later at the University of California, San Diego, Ian supervised a number of students through their PhD degrees, including Len Fisk and Tom Holzer (later to be NASA Associate Administrator and Director of the High Altitude Observatory in Boulder respectively).
Not surprisingly, Sir Ian became editor of the Journal of Geophysical Research in 1969, introducing a number of innovations that persist to this day, including the use of at least two referees and their identification. Under his leadership, the JGR was propelled to its current preeminence. During this period, Ian was prominent in helping lay the groundwork for future space missions, many of which came to fruition a decade or more later. This included what later came to be the Voyager missions, originally conceived of as the Mariner-Jupiter- Saturn missions. It was at this time too that the first out-of-ecliptic mission was conceived as part of a coordinated plan to explore the outer solar system. This became of course the equally successful Ulysses mission.
With the new missions, Ian's interests gravitated a little towards the magnetospheres of the outer planets, especially their interactions with the active moons. The Voyager missions were rightly regarded by Ian as one the greatest scientific-cultural achievements of the 20th century and he was a strong advocate and supporter of the program. The breadth of Ian's scientific interests is reflected in virtually every aspect of the Voyager mission, from the various planetary magnetospheres, their moons and interactions, particle acceleration, all the way to the nature of the solar wind interaction with the interstellar medium. His 1972 review of the solar wind - LISM interaction was the standard in the field for decades and the prescience of his views on the importance of interstellar neutral hydrogen in shaping the physics and structure of the large-scale heliosphere only came to be fully appreciated in the mid-1990's.
Ian's stay at UCSD ended in 1974 when he was appointed, at the age of 41, to the position of Director of the Max-Planck-Institute of Aeronomy (MPAe) in Kattlenburg-Lindau, Germany. There is little doubt that Ian had a transformational effect on the MPAe, drawing an international cast of visiting scientists and propelling the institute into multiple spacecraft missions. For many, the MPAe became for a time very much one of the world-leading centers for space physics and planetary physics, and many of us came of age scientifically in Katlenburg-Lindau, spending time working with or drawing inspiration from Ian. We well recall the afternoon tea times spent on a somewhat overused and shabby couch in front of a blackboard in the refectory, trying to formulate mathematically some problem or other. This was a wonderful time and wonderful way of doing science, which sadly appears to be disappearing from our scientific culture.
The spacecraft missions that Ian was especially involved with during his time at the MPAe included Ulysses, the cometary mission Giotto, and SOHO. These missions were outstandingly successful scientifically, but their genesis and shepherding to successful launches demanded skills at an international political level that were very demanding. Ian's stature and his dual US-European perspective proved invaluable in ensuring that these missions became the success that they were. One of the great legacies from these missions, especially Giotto, was the drawing of smaller countries without a strong space physics tradition, such as Ireland, into major spacecraft missions. This had a tremendously stimulating effect across Europe. These administrative and political activities of course drew heavily on his time, but he still found time to pursue some of his scientific interests. Among his most important contributions in his later career was, as mentioned above, his elucidation of the diffusive shock acceleration mechanism that is now thought to operate at collisionless shock waves. This work in many ways epitomizes Ian - in discovering the idea of diffusive shock acceleration, Ian drew from his extraordinary knowledge of cosmic ray transport, and his deep understanding of shock waves and MHD. It is probably no exaggeration to suggest that perhaps nearly 80% of published papers in space- and astrophysics discussing particle energization rely on the diffusive shock acceleration mechanism, illustrating the remarkable fruitfulness of Ian's many ideas. Ian also contributed in 1999 to a mechanism, now highly favored, of explaining non-thermal X-rays from clusters of galaxies. Sir Ian retired from the MPAe as Director in 2001. During his time as Director of MPAe, Ian also served as Vice-Chancellor at Victoria University in Wellington from 1982. Here he led the creation of the research school of earth sciences and encouraged the development of the Institute of Policy Studies and the Stout Research Centre. Ian continued to be active for some years after retirement, accepting the Pei-Ling Chan Chair of Physics at the University of Alabama in Huntsville (2002-04), as well as spending a number of months each year at the University of California, Riverside and the MPAe. In addition to science, Ian took a considerable interest in history, co-authoring an interesting book ("In Soso's Web") with Tamara Breus about life in the USSR.
Given Ian's extraordinary career track, he was the recipient of numerous honors and prizes. At the remarkably young age of 39 (1972), he was awarded the John Adams Fleming medal by the AGU. Other notable international awards include the Space Science Award by the American Institute of Aeronautics and Astronautics (1970), the Tsiolkovsky Medal by the Kosmonautical Federation of the USSR (1987) the Chapman Medal by the Royal Astronomical Society (1994), and the New Zealand Science and Technology Gold Medal (1994). Ian was greatly honored in New Zealand, receiving awards and honors not typical of an ordinary scientist. Ian was awarded New Zealand's top science honor, the Rutherford Medal, in 1995, "for his excellent contribution to fundamental research which has led to a deeper understanding of the nature of planetary magnetospheres, comets, interplanetary space, the behaviour of interstellar gas and the origin of cosmic rays." At the end of 1995, he was made a Knight Bachelor - one of the last under the imperial system before the introduction of New Zealand honors - one year after being named New Zealander of the Year ... Ian also led a number of international organizations, serving as president of COSPAR, the Space Research Committee of the International Council of Scientific Unions, and the European Geophysical Society, and was vice-president of the Asia- Oceania Geophysical Society. Finally, Ian was a foreign associate of the National Academy of Sciences in the United States, a fellow of the Academia Europaea, a fellow of the Royal Society, and a fellow of the American Geophysical Union.
G. Zank, J.F. McKenzie, and R. Lieu [AGU SPA Section Newsletter, 16 March 2010]