Magnetohydrodynamics dynamical relaxation of coronal magnetic fields. I. Parallel untwisted magnetic fields in 2D

Abstract

Context. For the last thirty years, most of the studies on the relaxation of stressed magnetic fields in the solar environment have onlyconsidered the Lorentz force, neglecting plasma contributions, and therefore, limiting every equilibrium to that of a force-free field. Aims. Here we begin a study of the non-resistive evolution of finite beta plasmas and their relaxation to magnetohydrostatic states, where magnetic forces are balanced by plasma-pressure gradients, by using a simple 2D scenario involving a hydromagnetic disturbance to a uniform magnetic field. The final equilibrium state is predicted as a function of the initial disturbances, with aims to demonstrate what happens to the plasma during the relaxation process and to see what effects it has on the final equilibrium state. Methods. A set of numerical experiments are run using a full MHD code, with the relaxation driven by magnetoacoustic waves damped by viscous effects. The numerical results are compared with analytical calculations made within the linear regime, in which the whole process must remain adiabatic. Particular attention is paid to the thermodynamic behaviour of the plasma during the relaxation. Results. The analytical predictions for the final non force-free equilibrium depend only on the initial perturbations and the total pressure of the system. It is found that these predictions hold surprisingly well even for amplitudes of the perturbation far outside the linear regime. Conclusions. Including the effects of a finite plasma beta in relaxation experiments leads to significant differences from the force-free case.

References in corpus (7)

• Preprocessing of vector magnetograph data for a non-linear force-free magnetic field reconstruction
• Non-linear force-free field modeling of a solar active region around the time of a major flare and coronal mass ejection
• The Number Of Magnetic Null Points In The Quiet Sun Corona
• A self-consistent nonlinear force-free solution for a solar active region magnetic field
• Can We Improve the Preprocessing of Photospheric Vector Magnetograms by the Inclusion of Chromospheric Observations?
• MHD mode coupling in the neighbourhood of a 2D null point
• Lagrangian relaxation schemes for calculating force-free magnetic fields, and their limitations

Cited by in corpus (4)

• Dynamical Relaxation of Coronal Magnetic Fields. III. 3D Spiral Nulls
• Magnetohydrodynamics dynamical relaxation of coronal magnetic fields. IV. 3D tilted nulls
• Magnetohydrodynamics dynamical relaxation of coronal magnetic fields. II. 2D magnetic X-points
• Consequences of spontaneous reconnection at a two-dimensional non-force-free current layer