Wednesday, March 13, 2013


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 

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]

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