2004ApJ...601..896B

The interaction of a supernova remnant with its surrounding environment is a powerful source of radiation in various spectral regions and at different stages in its development. The study of these emissions can therefore help to investigate the interstellar medium surrounding a supernova. For example, the highly asymmetric X-ray emission from PKS 1209-52 has previously been described as resulting from the supernova shock front on the eastern side of the remnant interacting with a small, dense interstellar cloud (or cloud core). In this paper we describe a possible mechanism through which the kinetic energy of the expanding shock is converted to energetic electrons. The particular interaction is a plasma streaming instability known as the modified two-stream instability that creates plasma waves in the lower hybrid frequency range that can then go on to accelerate electrons to high energy. A Fokker-Planck equation describing the diffusion of the electrons to high energies by lower hybrid waves is solved for both Gaussian and Lorentzian wave spectral distributions. We also simulate the interaction between the supernova remnant with the dense interstellar cloud using a two-dimensional fluid code. The nonthermal electrons can then generate X-ray emission via bremsstrahlung and also line radiation through interactions with the ambient medium. The maximum energy of these electrons is limited to the few keV energy range and therefore does not lead to any synchrotron radio emission that would otherwise lead to a radio asymmetry in the remnant that is not seen.