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Author: George Miloshevich
Requested Type: Poster
Submitted: 2017-03-10 14:10:22

Co-authors: Y. Kawazura, P. J. Morrison

Contact Info:
The University of Texas at Austin
110 Inner Campus Drive
Austin,   78705
United States

Abstract Text:
 In astrophysical and other applications, plasma is often in a collisionless state, where resistive and viscous effects are not important on the time/spatial scales of interest. Extended MHD (XMHD) is a one-fluid Hamiltonian theory endowed with 2-fluid effects, which are thought to be important for the formation of relativistic jets from active galactic nuclei, micro-quasars, and gamma-ray bursts.  Here we consider the relativistic [1] generalization of XMHD, obtained via an action principle (AP).  We describe covariant Poisson bracket in terms of Eulerian variables, with  constraints  implemented via the degeneracy of the Poisson bracket.  
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Another important result is the formulation of relativistic HMHD obtained by taking a limit of the AP for XMHD.  While nonrelativistic HMHD does not have a direct mechanism for collisionless reconnection, relativistic HMHD allows the violation of the frozen-in magnetic flux condition via an electron thermal inertia effect. An alternative frozen-in flux has also been found in a manner similar to that for nonrelativistic IMHD. The scale length of the collisionless reconnection is shown to correspond to the reconnection layer width estimated by the Sweet-parker model [2]. 

Finally, it is possible to pass to the nonrelativistic limit within the action itself while performing a 3+1 decomposition. This results in a bracket that is more general than the one derived earlier by Abdelhamid at al. [3], as it is valid for arbitrary electron to ion mass ratio and can be applied, for instance, to electron-positron plasmas. Further,  the Casmir invariants one obtains this way turn out to be precisely the generalized helicities, which topologically constrain possible evolution of the plasma.

[1] Y. Kawazura, G. Miloshevich, P. J. Morrison, Phys. Plasmas 24, 022103 (2017)

[2] L. Comisso and F. A. Asenjo, PRL 113, 045001 (2014) 

[3] H. M. Abdelhamid, Y. Kawazura, and Z. Yoshida, J. Phys.A  48, 235502 (2015)

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