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Session 74 - Supernova Remnants.
Display session, Thursday, June 13
Great Hall,

[74.15] The Magnetohydrodynamics of Supersonic Gas Clumps

I. L. Tregillis, T. W. Jones, D. Ryu (U. Minnesota)

We report 2D MHD simulations exploring the role and evolution of magnetic fields in the dynamics of supersonic plasma clumps. We examine the influence of both ambient field strength and orientation on the problem. Of those two characteristics, field orientation is far more important in the cases we have considered with \beta_o = p_g/p_b \ge 1. This is due to the geometry sensitivity of field stretching/amplification from large-scle shearing motions around the clump. When the ambient field is transverse to the clump motion, even a modest field, well below equipartition strength, can be amplified by field-line stretching around the clump, so that Maxwell stresses become comparable to the ram pressure on the clump. When the ambient field is aligned to the clump motion reconnection-prone topologies develop that shorten the field lines and release much of the energy it contains. In both cases, however, the presence of a field of even moderate initial strength acts to help the flow to realign itself around the clump into a smoother, less disruptive form. This work is supported by the NSF, by NASA and by the Univesity of Minnesota Supercomputer Institute.

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