Simple analytical examples of boundary driven evolution of a two-dimensional magnetohydrostatic equilibrium

Free access article

Issue		A&A Volume 507, Number 1, November III 2009


Page(s)		29 - 33
Section		Astrophysical processes
DOI		http://dx.doi.org/10.1051/0004-6361/200912942
Published online		15 September 2009

A&A 507, 29-33 (2009)
DOI: 10.1051/0004-6361/200912942

Simple analytical examples of boundary driven evolution of a two-dimensional magnetohydrostatic equilibrium

J. J. Aly

AIM – Unité Mixte de Recherche CEA – CNRS – Université Paris VII – UMR No 7158, Centre d'Études de Saclay, 91191 Gif-sur-Yvette Cedex, France
e-mail: jean-jacques.aly@cea.fr

Received 20 July 2009 / Accepted 1 September 2009

Abstract
Aims. We construct families of time-sequences of x-invariant magnetostatic equilibria which describe ideal quasi-static evolutions driven by stationary shearing motions imposed on a boundary. The change in the thermal pressure of the plasma is determined by imposing either an adiabatic, or an isothermal, or an isobaric, prescription.
Methods. We start from a well known family of linear force-free fields, on which we effect simple transforms.
Results. In either case, the magnetic field and the pressure are expressed analytically as functions of space and time. The field is found to suffer an indefinite expansion, with a decrease to zero of the pressure in the adiabatic and isothermal cases, and to eventually open. Moreover, the configurations forming any sequence are shown to be linearly stable with respect to x-invariant perturbations.

Key words: magnetohydrodynamics (MHD) -- Sun: magnetic fields -- Sun: corona -- Sun: coronal mass ejections (CMEs)

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