We record with sadness the death of Franz Kahn, a former Associate
Editor of
the Journal of Plasma Physics.Franz was born in Germany in 1926, but his family emigrated to England
in
1938. He attended Oxford University, obtaining First Class Honours in
Mathematics in 1947, and continuing as a research student there, eventually
gaining his D.Phil. in 1950. His thesis work already involved him in plasma
physics, under one of the pioneers of the subject. His supervisor was Sydney
Chapman, and his topic was that of the production of plasma by solar flares,
and its interaction with the Earth's atmosphere. This field had already
been
opened by Chapman and a previous pupil, Vincent Ferraro, in the 1930s.
The
idea had originally been phrased in terms of ‘corpuscles’,
i.e. energetic ions and
electrons, but it had gradually been realized that electrostatic forces
give such
a medium a coherence, so that it should be described as a fluid, notwithstanding
the lack of collisions. This is of course the basic idea of plasma physics,
and
when the importance of magnetic fields was included, one had all the
ingredients of magnetohydrodynamics.
Quasi–Static Evolution of Force–Free Magnetic Fields and a Model for Two–Ribbon Solar Flares
