Reconnection in a global model of Poincaré map describing dynamics of magnetic field lines in a reversed shear tokamak
✍ Scribed by E. Petrisor; J.H. Misguich; D. Constantinescu
- Publisher
- Elsevier Science
- Year
- 2003
- Tongue
- English
- Weight
- 489 KB
- Volume
- 18
- Category
- Article
- ISSN
- 0960-0779
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✦ Synopsis
Magnetic field lines behaviour in a reversed shear tokamak can be described by a one and a half degree of freedom Hamiltonian system. In order to get insights into its dynamics we study numerically a global model for a Poincar e e map associated to such a system. Mainly we investigate the scenario of reconnection of the invariant manifolds of two hyperbolic orbits of the same type n=m and show that it is a generic one. When the two Poincar e e-Birkhoff chains involved in this process are aligned in phase, i.e. they are in a nongeneric position, a sequence of two saddle-center bifurcations occur in one of the chains, interfering with the former elliptic orbit of that chain, such that at the reconnection threshold the two chains are in a generic position. Dynamics around the new created configuration at the reconnection appears to vary from a regular motion to a chaotic one.
In connection with the study of this global bifurcation we give the first example of region of instability in the dynamics of a nontwist map.