Minimum Dissipative Processes in Laboratory and Astrophysical Plasmas

Details Minimum Dissipative Processes in Laboratory and Astrophysical Plasmas Minimum Dissipative Processes in Laboratory and Astrophysical Plasmas

Dec 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufmng43a1206j&link_type=abstract

American Geophysical Union, Fall Meeting 2009, abstract #NG43A-1206

Astronomy and Astrophysics

Astrophysics

[4485] Nonlinear Geophysics / Self-Organization, [7509] Solar Physics, Astrophysics, And Astronomy / Corona

Scientific paper

The usual theory of plasma relaxation, based on selective decay of magnetic energy over the (global) magnetic helicity predicts a force-free state for a plasma. Such force-free state is often unrealistic in nature, an alternative theory of relaxation has been proposed by many authors, which is based on a well-known theorem of irreversible thermodynamics, principle of minimum entropy production rate. This is equivalent to minimum dissipation rate of energy. To demonstrate this, we perform self-consistent, time-dependent numerical simulations of dissipative plasmas at a higher Landquist number, typically ~ O(106-107), using full three dimensional compressible MHD code with a numerical resolution of 1283. Our simulations follow the time variation of global helicity, magnetic energy, and the dissipation rate and show that the global helicity remains approximately constant while magnetic energy is decaying faster and dissipation rate is decaying even faster than the magnetic energy. Existence of a perpendicular component of current is also demonstrated. We describe the application of our model to various laboratory plasma devices, like, Reversed Field Pinch (RFP) Tokamak, Field Reversed Configurations (FRC) and Spheromak. Using a two fluid description, we also show that Solar arcade structures can be modeled as a minimum dissipative relaxed state, and different types of arcade structures are generated with the variation of a single parameter characterizing the relaxed state. Finally, we outline a novel approach to non-force free coronal magnetic field extrapolation from vector magnetograms.

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