2014/12/02 by B. C. Low · 1 citation
Biochemistry, Genetics and Molecular Biology · Physics and Astronomy · #Field (mathematics) #Geomagnetism and Paleomagnetism Studies #Induction equation #Inviscid flow #Ionosphere and magnetosphere dynamics #Lorentz force #Magnetic field #Magnetic flux #Magnetohydrodynamics #Solar and Space Plasma Dynamics #Topology (electrical circuits) #Vortex #astro-ph.SR
paper · pdf · doi:10.1007/s11433-014-5626-7
published as Science China - Physics, Mechanics and Astronomy 2015 Vol. 58 No. 1: 015201 · Review article, 20 pages, 2 figures, 158 references. see http://download.hao.ucar.edu/pub/low/Low_Sci_China-Phys_Mech_Astron_2015_58-015201.pdf
openalex publication_date 2014/12/02 · arxiv created 2014/12/18 · arxiv updated 2014/12/22 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Magnetic field topology frozen in ideal magnetohydrodynamics (MHD) and its breakage in near ideal MHD are reviewed in two parts. The first part gives a physically complete description of the frozen in field topology, taking magnetic flux conservation as fundamental and treating four topics, Eulerian and Lagrangian descriptions of MHD, Chandrasekhar-Kendall and Euler-potential field representations, magnetic helicity, and inviscid vortex dynamics in comparison to ideal MHD. A corollary clarifies the challenge of achieving a high degree of the frozen in condition in numerical MHD. The second part treats field topology breakage centered on the Parker Magnetostatic Theorem on a general incompatibility of a continuous magnetic field with the dual demand of force free equilibrium and an arbitrarily prescribed, 3D field topology. Preserving field topology as a global constraint readily results in formation of tangential magnetic discontinuities, i.e., electric current sheets of zero thickness. A similar incompatibility is present in the steady, force and thermal balance of a heated radiating fluid subject to an anisotropic thermal flux conducted strictly along the frozen in magnetic field in the low beta limit. In a weakly resistive fluid the thinning of current sheets by these incompatibilities inevitably results in sheet dissipation, resistive heating and topological changes in the field despite the small resistivity. Faraday induction drives but also macroscopically limits this mode of energy dissipation, storing free energy in self organized, ideal MHD structures. This property of MHD turbulence captured by the Taylor hypothesis is reviewed in relation to the Sun's corona, calling for a basic quantitative description of the breakdown of flux conservation in the low resistivity limit. A cylindrical, initial boundary value problem provides specificity in the review.