Gamma-Ray Bursts

Jonathan I. Katz, Professor


JONATHAN KATZ

[my last name]@wuphys.wustl.edu

 

Professor Katz's work, originally mostly in astrophysics, now involves a number of diverse topics in applied physics, biophysics, materials science, energy and the environment. His complete publication list should be consulted for details.

Following the blow-out of the Macondo well in the Gulf of Mexico (April 20, 2010) Prof. Katz was appointed to Secretary of Energy Chu's scientific advisory panel. This experience led him to conceive a novel composition of drilling mud, involving a dilatant polymer that could make the mud viscoelastic, in order to suppress instabilities that would otherwise occur. In collaboration with Richard Garwin (also on the panel) he predicted that attempts at ``top kill'' with conventional muds would only lead to that mud being spat out the well-head with the escaping oil. This prediction was borne out when top kill was attempted with conventional muds and failed. Prof. Katz then organized, in collaboration with Peter Beiersdorfer and his team at the Lawrence Livermore National Laboratory, an experimental effort to test the prediction that a viscoelastic mud would not suffer such instabilities. The prediction was verified, and a paper reporting these results has been published in Physical Review Letters (106, 058301 [2011]).

In astrophysics Prof. Katz is studying the scaling laws that govern the behavior of accretion discs around black holes. These range over eight orders of magnitude in the mass of the black hole, from the stellar mass black holes in black hole binary stars to the supermassive black holes in active galactic nuclei (quasars) and blazars. Their accretion rates range over more than sixteen orders of magnitude, from the rates seen in mass-transfer binary star X-ray sources to those of gamma-ray bursts. Accretion discs around black holes display a bewildering array of phenomenology, very little of which is understood on fundamental physical grounds, and the use of scaling laws is one possible means of organizing this phenomenology. One common feature, found over a broad range of parameters, is the conversion of gravitational (accretion) energy to the acceleration of energetic particles. The fundamental process is the action of a unipolar dynamo, as found in radio pulsars and the magnetosphere of Jupiter, even though those do not contain accretion discs. He has inferred that at sufficiently high power densities, as are found in gamma-ray bursts, an equilibrium pair plasma of MeV temperatures is produced instead (in gamma-ray bursts this plasma later converts its energy back to particle acceleration in a collisionless shock). This has led to the prediction, so far untested, that very fast, high field pulsars would produce a wind of pair plasma rather than a much smaller number of very energetic particles.

Prof. Katz has studied the problem of geoengineering to counteract the warming effects of anthropogenic carbon dioxide by introducing artificial scattering aerosols into the stratsophere. This is an old idea, inspired by the observation of cooling following large volcanic eruptions that loft sulphur oxides to the stratosphere where they form sulfuric acid droplets, a connection first noted by Benjamin Franklin. He has investigated the questions of determining the best material to use, the best form in which to loft it, and the best means of lofting. The tentative answers are sulfur, liquid hydrogen sulfide and rockets. In any such scheme questions of chemical kinetics arise that are not important in natural volcanic injection.

In a related project, Prof. Katz has developed a simple pedagogical one-equation greenhouse warming model controlled by the infrared opacity of water vapor, the most important greenhouse gas. In this model the climate is generally intrinsically unstable, with two stable limit points, glaciation and warm interglacials. Then our present intermediate state can only be maintained by continual geoengineering, with or without anthropogenic greenhouse gases.

Prof. Katz has recently turned his attention to climate change. He and an undergraduate, Thomas Muschinski (who suggested this direction for his Senior Thesis) defined a new measure of "storminess" and calculated it from NOAA hourly rainfall data at 13 sites in the 48 contiguous United States during the 20th Century epoch of warming. They found a significant steady increase in storminess at a site on the Olympic Peninsula (known for frequent steady drizzle, rather than storms) and were able to set upper bounds on any steady trends in storminess at the other 12 (stormier) sites. These results are in press as a joint paper in Nature Climate Change (2013).

Prof. Katz is working on problems in boundary layer hydrodynamics. He analyzed the process of rapid adiabatic blowdown of a pressure vessel, and derived a novel dimensionless number describing the importance of buoyancy-driven circulation, resulting from the competition between conductive heating of the gas near the wall and the adiabatic cooling of the gas in the interior of the vessel. He is now working on double-diffusive boundary layers, such as those between water and glycerin or plasmas of different composition in laser-fusion targets, in which both momentum and mass diffuse, and in which the composition (affected by mass diffusion) affects the viscosity (that determines the diffusion of momentum).

In collaboration with Prof. James G. Miller of the Washington University Laboratory for Ultrasonics, Prof. Katz is developing an experimental program in the rheology of suspensions and soft matter. This follows his work on the use of corn starch suspensions as possible oil well kill fluids (described above). A portion of this effort concerns the rheology of these suspensions. For example, they are trying to determine why aqueous suspensions of corn starch show the striking phenomenon of discontinuous shear thickening (familiar to children), while most other suspensions, including oil suspensions of corn starch, show shear thinning. This is being pursued with rheological measurements of oil suspensions, both confined and unconfined, to determine if the difference is a consequence of the different surface interactions of starch granules with oil and water. In addition, apparatus is being developed to measure the structure factor (spatial distribution) of granules in sheared suspensions using scattering of ultrasound, whose wavelengths are matched to the sizes and spacing of the granules. This microstructure determines the rheological properties of the suspensions, and is difficult to probe in any other manner.

In collaboration with the work of Prof. Miller's group on the ultrasonic properties of trabecular (spongy) bone, Prof. Katz developed a model for the mechanical properties of networks of rods connecting random nodes. This model involves the novel concept of wavelength-dependent elastic moduli, showed that trabecular bone more closely resembles foams, and offers a path towards making extraordinarily stiff porous structures.

Some past highlights:

Invention of model of precessing accretion discs found in most mass transfer binary stars (Nature Phys. Sci. 246, 87 [1973]).

First recognition of importance and implications of X-ray sources in globular clusters (Nature 253, 698 [1975]).

Explanation of astronomical Soft Gamma Repeaters as resulting from dissipation of magnetic energy (now known as the "Magnetar" model) (Ap. J. 260, 371 [1982]).

Invention of model, later popularized by Bak as "Self-organized criticality", now applied in many branches of science (J. Geophys. Res. 91, 10412 [1986]).

First prediction of gamma-ray burst afterglows, confirmed 1987 (Ap. J. Lett. 432, L107 [1994]).

 

"The Biggest Bangs," J. I. Katz, Oxford U. Press (2002); is a popular book about gamma-ray bursts. To see excerpts (the Table of Contents and a sample chapter) click on your preferred format:  postscript  pdf.


Complete Publication List

Vita

High Energy Astrophysics (Addison-Wesley, 1987)

Other items of possible interest, meant to be thought-provoking:

Washington University Press Policy

Nature Cannot be Fooled

Limiting the Nuclear Club---Iraq, North Korea, et al. 1994 article published in Strategic Review advocating pre-emptive strike against North Korea's nuclear weapons project

Don't Become A Scientist!

Anyone Who Bombs Baghdad [when Saddam was in power] Gets My Vote

Saddam's Options

Diversity is the Last Refuge of a Scoundrel

Earthquake-safe Housing for Iran and Elsewhere

The Summers Affair

What is Political Correctness?

Deception and Denial in Iraq and the Intelligent Adversary Corollary

Hurricane Mitigation with Surfactants

The North Korean Bomb

Why Terrorism is Important

Cold Thoughts on Global Warming

Is Your Drywall Making You Sick?

Errata for Panofsky and Phillips Classical Electricity and Magnetism 2nd ed. (Most of these are on an errata page in the Dover reprint.)

Viscoelastic Suppression of Gravity-Driven Counterflow Instability This paper by P. Beiersdorfer, D. Layne, E. W. Magee and J. I. Katz reports experiments on surrogate drilling muds shear-stiffened with corn starch. These might have enabled "top kill" of the blown-out Macondo oil well in the Gulf of Mexico in May 2010, rather than July. Also at: .