Casolari, A. and Pucella, G. (2017) Numerical investigation of tearing modes amplitude oscillations. Il nuovo cimento C, 40 (2). pp. 1-10. ISSN 1826-9885
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Abstract
A recently observed phenomenon involving magnetic islands in high-density pulses in the Frascati Tokamak Upgrade is investigated using numerical simulations in slab geometry. This phenomenon was given the name “limit cycles” because of the figure drawn by the trajectory of the system in the amplitude/frequency plane of magnetic islands. In this regime of propagation, the magnetic islands show a quasi-periodic modulation of their amplitude and rotation frequency. The Fourier analysis of the experimental signals shows a large harmonic content, which we ascribed to a significant island deformation in the cycle phase. We performed a series of numerical simulations by integrating a four-field system of equations through a finite difference code to check this hypothesis. The results of the simulations show that a large density gradient causes a significant island deformation in the nonlinear regime, in agreement with our hypothesis. This deformation is caused by the diamagnetic velocity shear resulting from the nonlinear flattening of the density profile inside the island separatrix.
| Item Type: | Article |
|---|---|
| Subjects: | 500 Scienze naturali e Matematica > 530 Fisica |
| Depositing User: | Marina Spanti |
| Date Deposited: | 17 Nov 2020 09:39 |
| Last Modified: | 17 Nov 2020 09:39 |
| URI: | http://eprints.bice.rm.cnr.it/id/eprint/19904 |
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