Anisotropic viscous dissipation in compressible magnetic X-points
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.
Permanent Research Commons link: http://hdl.handle.net/10289/2755
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.
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This article is published in the journal: Astronomy and Astrophysics. © ESO 2008.