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J. P. Foy, J. J. Hester (Arizona State University)
We present 1-D MHD numerical simulations of the 'wisps' in the Crab Synchrotron Nebula, including energy losses due to synchrotron radiation. Hubble Space Telescope and Chandra X-Ray observations of the Crab Synchrotron Nebula confirm that the ring-like features called 'wisps' are dynamic structures that move outward from the pulsar at relativistic speeds. The wisps form, sharpen and disperse on a time scale of weeks to months, decelerating as they propagate outward (Hester, J.J. 1998, Mem. Soc. Astron. Italiana, 69, 883, and Hester et. al. 2001, ApJ, 557, L49). Following the suggestion of these authors, we hypothesize that the wisps are the result of a synchrotron cooling instability. Particles, whose outflow momenta is randomized at a shock in a magnetized electron-positron plasma, lose energy as they emit synchrotron radiation at nearly constant pressure thereby causing a compression of field lines and a resulting enhancement in emission from the wisp structures. This mechanism requires that the post-shock pressure is carried by the most energetic particles with short synchrotron lifetimes. We present preliminary results of efforts to model this process by including synchrotron losses in a calculation of the post-shocked flow in the pulsar wind.
J.P.F. acknowledges support from the Arizona State University NASA Space Grant Program.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.