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Session 37 - New Light on Supernovae Remnants.
Oral session, Wednesday, June 11
North Main Hall F/G,
I review nonlinear theories of particle acceleration in strong collisionless shocks, and their implications for nonthermal emission from supernova remnants, particularly at infrared and shorter wavelengths. Nonlinear theories predict higher shock compression ratios as well as spectral curvature in the accelerated-particle distributions. Electron acceleration to energies in excess of 1 TeV is expected in most theories of shock acceleration, so that nonthermal continua from infrared to soft X-rays can be significant. In young remnants with high shock velocities, significant synchrotron emission up to 10 keV and above can be produced. In addition, nonthermal bremsstrahlung from the lowest-energy superthermal electrons, where the electron population begins to deviate from a pure Maxwellian, may contribute at energies above a few keV. Gamma-ray emission from supernova-remnant shock waves can arise from either the proton or electron component of cosmic rays: protons interact with thermal gas to produce \pi^0 mesons which decay to gamma rays, while electrons can scatter microwave-background photons to produce inverse-Compton gamma rays. If the hadronic processes can be shown to dominate, confirmed gamma-ray detection of supernova-remnant shock waves will mean the first direct, in situ verification of shock acceleration of ions to relativistic energies. Finally, I shall review new work on grain acceleration in supernova-remnant shocks which gives an excellent description of relative cosmic-ray abundances of different ion species. I discuss observational predictions for these important new avenues for investigating the physics of strong shock waves and particle acceleration in supernova remnants.
Program listing for Wednesday