Computation of three-dimensional MHD equilibria with current sheets and magnetic islands
Event details
| Date | 15.06.2015 |
| Hour | 10:30 |
| Speaker | Dr. J. Loizu, Max Planck Princeton Center for Plasma Physics, USA |
| Location |
PPB 019
|
| Category | Conferences - Seminars |
The theory and numerical computation of three-dimensional MHD equilibria is of fundamental importance for understanding the behaviour of both magnetically confined fusion and astrophysical plasmas. In particular, ideal MHD predicts the existence of singular current densities forming at rational surfaces in three-dimensional equilibria with nested surfaces, thus making non-smooth solutions ubiquitous to the 3D MHD problem. These current sheets play a crucial role in the describing (1) the plasma response to non-axisymmetric boundary perturbations, (2) the ideal and resistive stability of magnetically confined plasmas, and (3) the dynamics of reconnection phenomena, such as sawteeth.
While analytical formulations have been developed to describe such currents in simplified geometries, a numerical proof of their existence has been hampered by the assumption of smooth functions made in conventional MHD equilibrium models such as VMEC. Recently, a theory based on a generalized energy principle, referred to as multi-region, relaxed MHD (MRxMHD), was developed and incorporates the possibility of non-smooth solutions to the MHD equilibrium problem.
Using SPEC, a nonlinear implementation of MRxMHD, we provide the first numerical proof of their mutual existence [1] and a novel theoretical guideline for the numerical computation of three-dimensional ideal MHD equilibria with current sheets [2].
[1] J. Loizu, S. Hudson, A. Bhattacharjee and P. Helander, Phys. Plasmas 22 022501 (2015)
[2] J. Loizu, S. Hudson, A. Bhattacharjee and P. Helander, submitted (2015)
While analytical formulations have been developed to describe such currents in simplified geometries, a numerical proof of their existence has been hampered by the assumption of smooth functions made in conventional MHD equilibrium models such as VMEC. Recently, a theory based on a generalized energy principle, referred to as multi-region, relaxed MHD (MRxMHD), was developed and incorporates the possibility of non-smooth solutions to the MHD equilibrium problem.
Using SPEC, a nonlinear implementation of MRxMHD, we provide the first numerical proof of their mutual existence [1] and a novel theoretical guideline for the numerical computation of three-dimensional ideal MHD equilibria with current sheets [2].
[1] J. Loizu, S. Hudson, A. Bhattacharjee and P. Helander, Phys. Plasmas 22 022501 (2015)
[2] J. Loizu, S. Hudson, A. Bhattacharjee and P. Helander, submitted (2015)
Practical information
- Informed public
- Free
Organizer
- Prof. P. Ricci
Contact
- Prof. P. Ricci