Proceedings of the National Academy of Sciences of the United States of America

About the PNAS Member Editor
Name Balbus, Steven A.
Location University of Oxford
Primary Field Astronomy
Secondary Field Physics
 Election Citation
Balbus conceived the solution to a fundamental problem in astrophysics, the mechanism by which disks are able to accrete matter, and with Hawley demonstrated the validity of this mechanism by numerical simulation. More generally, he showed that extremely weak magnetic fields change the classical stability criteria for fluids.
 Research Interests
Steven Balbus' research interests span a broad range of topics in theoretical astrophysics. Early work included investigations of heating and cooling processes in the interstellar medium and gasdynamical processes in spiral galaxies. Since the early 1990's Balbus has been studying turbulence in accretion disks in many different astrophysical environments. How the Keplerian gas flow in such disks degenerates into turbulence, as observations strongly imply, had been a major problem in astrophysics. In a series of papers starting in 1991, Balbus and J. Hawley showed that the presence of any weak magnetic field in a rotating gas leads to a rapid instability, if the rotation rate of the gas decreases radially outwards. This is a much less stringent requirement than the classical Rayleigh criterion that the specific angular momentum decrease outwards. Subsequent computer simulations revealed the transition from laminar to turbulent flow, and the field of numerical accretion disk studies began. Balbus developed these ideas further, showing how weak magnetic fields profoundly affect the stability of dilute plasmas yet more generally. He has made important contributions to the theory of the Sun?s internal rotation, and has recently ventured into a very different field: how palaeozoic ocean tides may have influenced vertebrate evolution.

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