An energy formula for nonlinear forcefree magnetic fields
Abstract
This paper describes the relation between energy and helicity integrals for nonlinear forcefree fields, given arbitrary boundary conditions. First, the author reviews the relation of helicity integrals to structural properties of a field such as twist and shear. Helicity injection into an atmosphere due to boundary motions is also discussed. A gaugeinvariant fieldline helicity is defined which measures the net twisting of magnetic flux about a given fieldline. The author then presents a formula for the energy of a forcefree field in termns of these fieldine helicities. An expression for the energy of arbitrary fields, in terms of linking between magnetic fieldlines and the electrical current, is also given.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 August 1988
 Bibcode:
 1988A&A...201..355B
 Keywords:

 ForceFree Magnetic Fields;
 Magnetic Flux;
 Solar Atmosphere;
 Solar Magnetic Field;
 Energy Distribution;
 Magnetic Field Configurations;
 Magnetohydrodynamics;
 Photosphere;
 Solar Physics