Neutral and nonneutral collisionless plasma equilibria for twisted flux tubes: The GoldHoyle model in a background field 

Oliver Allanson Submitted: 20160915 08:29
We calculate exact onedimensional collisionless plasma equilibria for a continuum of flux tube models, for which the total magnetic field is made up of the ?forcefree? GoldHoyle magnetic flux tube embedded in a uniform and antiparallel background magnetic field. For a sufficiently weak background magnetic field, the axial component of the total magnetic field reverses at some finite radius. The presence of the background magnetic field means that the total system is not exactly forcefree, but by reducing its magnitude, the departure from forcefree can be made as small as desired. The distribution function for each species is a function of the three constants of motion; namely, the Hamiltonian and the canonical momenta in the axial and azimuthal directions. Poisson's equation and Ampère's law are solved exactly, and the solution allows either electrically neutral or nonneutral configurations, depending on the values of the bulk ion and electron flows. These equilibria have possible applications in various solar, space, and astrophysical contexts, as well as in the laboratory.
Authors: O. Allanson, F. Wilson & T. Neukirch
Projects: None

Publication Status: Physics of Plasmas, 23, 092106 (2016) [13 pages, Open Access]
Last Modified: 20160917 07:04



An exact collisionless equilibrium for the ForceFree Harris Sheet with low plasma beta 

Oliver Allanson Submitted: 20160908 07:01
We present a first discussion and analysis of the physical properties of a new exact collisionless equilibrium for a onedimensional nonlinear forcefree magnetic field, namely, the forcefree Harris sheet. The solution allows any value of the plasma beta, and crucially below unity, which previous nonlinear forcefree collisionless equilibria could not. The distribution function involves infinite series of Hermite polynomials in the canonical momenta, of which the important mathematical properties of convergence and nonnegativity have recently been proven. Plots of the distribution function are presented for the plasma beta modestly below unity, and we compare the shape of the distribution function in two of the velocity directions to a Maxwellian distribution.
Authors: O. Allanson, T. Neukirch, F. Wilson and S. Troscheit
Projects: None

Publication Status: Physics of Plasmas, 22, 102116 (2015) [11 pages, Open Access])
Last Modified: 20160910 13:41




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