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Session 44 - New Light on Supernova Remnants.
Display session, Wednesday, June 11
South Main Hall,
When a supernova-remnant blast wave encounters dense neutral or molecular gas, it is preceded by a precursor ionized by UV and soft X-ray flux from the hot postshock gas. The MHD waves invoked for the scattering necessary for particle acceleration can only exist in this precursor; cosmic rays that diffuse to the edge of it can escape freely into the neutral medium upstream. Nonlinear models of shock acceleration can predict the spectrum of these escaping cosmic rays, which stream out into the dense interstellar medium, partly ionizing it through collisions. If the acceleration is efficient, a significant fraction of the supernova energy can be deposited in ionization and heating far ahead of the blast wave itself. We present numerical calculations of this ionization under different assumptions about the escaping cosmic-ray spectrum. The observational inference that in some SNRs neutral material can survive all the way to the shock provides an upper limit to the escaping energetic-particle flux.
Program listing for Wednesday