Nonlinear force-free models for the solar corona

Magnetic Energy and Helicity Budgets in the Active-Region Solar Corona. I. Linear Force-Free Approximation

We self-consistently derive the magnetic energy and relative magnetic helicity budgets of a three-dimensional linear force-free magnetic structure rooted in a lower boundary plane. For the potential magnetic energy we derive a general expression that gives results practically equivalent to those of the magnetic Virial theorem. All magnetic energy and helicity budgets are formulated in terms of ...

Magnetic-Field Confinement in the Solar Corona. I. Force-Free Magnetic Fields

Axisymmetric force-free magnetic fields external to a unit sphere are studied as solutions to boundary value problems in an unbounded domain posed by the equilibrium equations. It is well known from virial considerations that stringent global constraints apply for a force-free field to be confined in equilibrium against expansion into the unbounded space. This property as a basic mechanism for ...

Reconstruction of Nonlinear Force-free Fields and Solar Flare Prediction

A brief review is presented of methods for calculating nonlinear force-free fields, with emphasis on a new, fast current-field iteration procedure. The motivation is to reconstruct coronal magnetic fields using high resolution vector magnetic field boundary data from a new generation of spectro-polarimetric instruments. Methods of solar flare prediction are also reviewed, with focus on the need...

Reconstruction of Solar Coronal Linear Force-Free Magnetic Field

A self-consistent nonlinear force-free solution for a solar active region magnetic field

Nonlinear force-free solutions for the magnetic field in the solar corona constructed using photospheric vector magnetic field boundary data suffer from a basic problem: the observed boundary data are inconsistent with the nonlinear force-free model. Specifically, there are two possible choices of boundary conditions on vertical current provided by the data, and the two choices lead to differen...