Magnetostatic atmospheres possessing identical invariants of ideal magnetohydrodynamics
Abstract
A physical analysis is presented of two distinct families of two-dimensional (2D) analytical solutions for isothermal periodic magnetostatic atmospheres in uniform gravity, one arrived at by Dungey and the other arrived at by Low and Manchester. It is demonstrated that particular members of the two families of 2D equilibria may be generated from the same planar state by plasma displacements which move the system through continuous sequences of equilibria while ensuring flux freezing. The two families of solutions both possess undulating magnetic field lines but geometrically different flux surfaces. The Dungey solutions can be created from a planar state by an undulating deformation whose spatial variation is along the field lines. By contrast, the 2D plane of variation of the Low-Manchester solutions lies at an angle to the field lines of the planar state. As a result, a mixed mode of undulating, interchange and shearing displacements must be made to the planar state to produce the more complex 2D state. Finally, the physical properties of these topologically equivalent states, including the magnetic and electrical helicities and the hydromagnetic potential energy, as introduced by Mouschovias, are discussed in terms of the variational principles of Kruskal and Kulsrud.
- Publication:
-
Physics of Plasmas
- Pub Date:
- April 2000
- DOI:
- 10.1063/1.873937
- Bibcode:
- 2000PhPl....7.1263M
- Keywords:
-
- 95.30.Qd;
- 47.65.+a;
- 41.20.Gz;
- Magnetohydrodynamics and plasmas;
- Magnetostatics;
- magnetic shielding magnetic induction boundary-value problems