Transition to the radiative phase in supernova remnant evolution

Details Transition to the radiative phase in supernova remnant evolution Transition to the radiative phase in supernova remnant evolution

Nov 1999

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999phdt........23w&link_type=abstract

Thesis (PhD). NORTH CAROLINA STATE UNIVERSITY, Source DAI-B 60/09, p. 4660, Mar 2000, 117 pages.

Astronomy and Astrophysics

Astrophysics

Scientific paper

The evolution of a supernova remnant (SNR) through the transition from an adiabatic Sedov-Taylor blastwave to a radiative pressure-driven snowplow phase is studied through a series of one-, two- and three-dimensional hydrodynamic (HD) and magnetohydrodynamic (MHD) simulations. This transition is marked by a catastrophic collapse of the postshock gas, forming a thin, dense shell behind the forward shock. Previous studies have shown that the thin, dense shell of gas present during this transition is susceptible to both radiative and dynamical instabilities. One-dimensional HD studies indicate the presence of a radial oscillation between the forward shock and the thin shell, due to the rapid cooling of the gas in the immediate postshock region. Two-dynamical HD simulations of this transition indicate the presence of violent dynamical instabilities that alter the initially spherical morphology of the blastwave, specifically, the Pressure-driven Thin Shell Overstability (PDTSO) and the Non-linear Thin Shell Instability (NTSI). Hydrodynamical simulations, by their very nature, ignore the effects of magnetic forces on moving fluids. In general, interstellar magnetic fields will be weak enough that their effects may be safely ignored. However, the transition to the radiative phase in SNR evolution is often triggered when the blastwave interacts with dense clouds of gas in the interstellar medium (ISM). The resulting compression of the gas during the transition also compresses the magnetic fields in the cloud, possibly enhancing the field sufficiently to play a role in the further evolution of the SNR. To better understand the role of the NTSI during the transition, and to study the effects of magnetic fields on the instability itself, we performed idealized two- and three-dimensional MHD simulations. The results of the two-dimensional simulations were found to depend strongly on the orientation of the ambient magnetic field when the postshock field is dynamically significant. To accurately model the evolution of the NTSI, only three-dimensional simulations will suffice. However, the three-dimensional simulations performed were unable to run long enough to detect characteristic exponential growth of the NTSI, but initial studies indicate the presence of the instability.

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