Issue |
A&A
Volume 487, Number 3, September I 2008
|
|
---|---|---|
Page(s) | 1155 - 1161 | |
Section | The Sun | |
DOI | https://doi.org/10.1051/0004-6361:200809960 | |
Published online | 01 July 2008 |
Anisotropic viscous dissipation in compressible magnetic X-points
Department of Mathematics, University of Waikato, PB 3105, Hamilton, New Zealand
Received:
14
April
2008
Accepted:
20
June
2008
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.
Key words: magnetohydrodynamics (MHD) / Sun: flares / Sun: magnetic fields / Sun: corona / plasmas
© ESO, 2008
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