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Anisotropic viscous dissipation in compressible magnetic X-points

Abstract
Context: Visco-resistive damping in line-tied magnetic X-points is examined. Aims: The goal is to determine whether fast, Alfvénic energy dissipation is possible for X-point disturbances damped by the plasma resistivity and non-isotropic viscosity. Methods: The response of X-points to planar and axial perturbations is explored numerically by solving the linearized compressible MHD equations in two and a half dimensions. Results: It is demonstrated that fast dissipation is possible in the case of non-reconnective planar disturbances damped by anisotropic viscosity in weakly resistive plasmas. Although perturbations which change the initial X-point topology decay slowly at large times when viscous effects are dominant, there is an initial phase in which a significant fraction of the disturbance energy is removed on an Alfvénic timescale. The decay of incompressive axial field disturbances occurs by a different mechanism, however, that is always formally slow (i.e. dependent on the small viscous and resistive damping coefficients). Conclusions: Computations suggest that fast, visco-resistive energy release in coronal plasmas is possible for compressive X-point disturbances. This result could have important implications for understanding rapid energy release in coronal active regions.
Type
Journal Article
Type of thesis
Series
Citation
Craig, I.J.D. (2008). Influence of the Hall effect on the reconnection rate at line-tied magnetic X-points. Astronomy & Astrophysics, 487(3), 1155-1161.
Date
2008
Publisher
E D P Sciences
Degree
Supervisors
Rights
This article is published in the journal: Astronomy and Astrophysics. © ESO 2008.