Mathematics – Logic
Scientific paper
Oct 1986
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1986inpr.conf...67d&link_type=abstract
In NASA. Ames Research Center Summer School on Interstellar Processes: Abstracts of Contributed Papers p 67-68 (SEE N87-15043 0
Mathematics
Logic
Clumps, Galactic Evolution, Stellar Envelopes, Stellar Evolution, Supernova Remnants, Magnetic Fields, Milky Way Galaxy, Morphology, Relativistic Plasmas, Shock Waves, Stellar Mass Ejection, Synchrotron Radiation
Scientific paper
Each of the youngest supernova remnants known in the Milky Way, Cas A, Kepler's SNR, and Tycho's SNR, shows a different morphological structure caused by different conditions in the progenitor stars and their surroundings. In all three cases, however, the observed shells have a thickness of about 1/4 the radius, a sharp outer edge, and significant brightness irregularities. These features require that the circumstellar medium be highly clumped. To investigate the phenomenon, models of the expansion have been constructed using a one-dimensional spherical hydrodynamic code. As a supernova shock moves down the external density gradient of the star, material behind the shock begins to go into free expansion. Then as surrounding material is encountered a reverse shock moving back into the ejectum will be formed. Until the expansion has swept up about eight times the ejected mass when the situation can be considered as a point explosion in its surroundings, the dynamics are controlled by conditions between the shocks. The region is also where the synchrotron radio emission from relativistic electrons trapped in magnetic fields arises. Initial particles and fields are accelerated and amplified by eddy motion at the interface between the ejected and swept-up material and at the boundaries of clumps. Polarimetry shows that these SNR have a net radial orientation of their magnetic fields apparently from stretching by Rayleigh-Taylor instabilities at the contact surfaces. Without clumps the observed shell is much too narrow and steep on the inside.
Dickel John R.
Eilek J. a.
Jones Michael E.
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