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Andrew F. Nelson

2005 Research Report

Dr. Nelson has recently embarked on a new project to model the evolution of massive circumstellar disks in the presense of both non-ideal equations of state and radiative heating and cooling. This project became possible due to his new association begun this year with the Los Alamos National Laboratory. A well developed numerical code including all such processes is in common use at the Lab, and must only be adapted to the problem of disk evolution. Work has begun on the adaptions necessary, but remains in an early phase, so that no results have yet been obtained. Nelson and his collaborators anticipate that the improved models will place significant constraints on conditions required to form Jovian planets via gravitational collapse in disks. In connection with his expertise in this area, Nelson recently participated in writing the review chapter on disk instabilities in circumstellar disks for the Protostars and Planets 5 review volume, which is intended for publication within the next year.

Dr. Nelson's most significant continuing project is to write and publish a general purpose SPH (Smoothed Particle Hydrodynamics) and N-body numerical code, for use by the community at large in studying astrophysical problems of interest on the serial and parallel computing platforms commonly available today. All benchmarks and timings for the code have now been completed, and we are generally pleased with the results. A set of two papers describing the code, its features and optimizations is well underway now, and is expected to be submitted it within the next couple of months. At that time, the code will also be released under the GNU General Public License.

At the time of last year's report, a paper defining numerical criteria required for the correct simulation of self gravitating disk system, had been submitted for publication and a generally favorable referee report returned. More substantial modifications were made than were requested, and a revised version resubmitted. The comments regarding the revised manuscript were much more critical however, and the paper remains unpublished, pending further revisions.

This year, Dr. Nelson's work to describe the dynamical properties of gas flowing around a forming Jovian planet core, has yielded an interesting and possibly very important side result, that the origin of a ubiquitous population of meteorites called chondrites may be linked to the formation of Jupiter itself. His results show that the dynamical evolution of the flow can produce rapid heating and cooling events through hydrodynamic shocks that are very similar to those expected to produce chondrules. An article in a refereed conference proceedings volume has been published describing these results.


Nelson, A. F., Ruffert, M., (2005) A proposed origin for chondrule-forming shocks in the solar nebula. ASP Conference Series: Chondrites and the Protoplanetary Disk. Volume 341, 903-912

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