Speaker
Marco Veranda
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.1060.pdf
Helical self-organization in 3D MHD modelling of fusion plasmas:
plasma flow effects and Alfvén waves detection
M. Veranda1, D. Bonfiglio1, S. Cappello1, L. Chacòn2, D. F. Escande3, A. Kryzhanovskyy1, M. Zuin1
1
Consorzio RFX (CNR, ENEA, INFN, Università degli Studi di Padova, Acciaierie Venete SpA), Padova, Italy
2
Los Alamos National Laboratory, Los Alamos, New Mexico, USA
3
Aix-Marseille Univ, CNRS, PIIM, UMR 7345, Marseille, France
Self-organized helical states are a ubiquitous feature in astrophysical and magnetic confinement current
carrying plasmas. In the reversed-field pinch toroidal plasmas quasi-helical states are observed both in
high current experiments [1] and in nonlinear magnetofluid numerical simulations [2]. In the tokamak
helical self-organization is an essential part of the dynamics in advanced regimes [3]. In this work we
show two main advancements in our 3D nonlinear visco-resistive magnetohydrodynamic (MHD)
studies. First, we study the effect of a macroscopic plasma rotation on helical states, to model both
reversed-field pinches and tokamaks: in particular, we analyze the interaction between an external
momentum source and/or seed magnetic perturbations (MPs), both static and rotating. We find the
expected interplay between plasma rotation and applied MPs in tokamaks [4] confirming MPs
screening over a threshold in normalized plasma rotation. We then focus on the reversed-field pinch
case: starting from previous works [5,6,7], where it is shown that a mean flow arises from and interacts
with nonlinearly coupled kink/tearing modes, and then introducing a momentum source, we analyse the
impact of mean plasma flow on self-organized helical regimes. Our modelling indicates that an external
momentum source of sufficiently high intensity can prevent the formation of a helical state, while a
moderate one is compatible with a slight enhancement of the intensity of the helical state. We present a
novel study in the realistic cases [2] of experimental-like helical states stimulated by MPs: the presence
of a plasma flow, previously not considered, introduces quantitative changes to their properties. As a
final novelty, we here also show (for the first time) that the typical intermittency with reconnection
events displayed in the RFP helical self-organization process is accompanied by the excitation of both
compressional and shear Alfvén waves, in reasonable agreement with experimental measurement [8].
References:
1 R. Lorenzini, E. Martines, P. Piovesan, et al, Nature Physics 5, 570 (2009)
2 M. Veranda, D. Bonfiglio, S. Cappello, et al., NF 57, 116029 (2017)
3 P. Piovesan, D. Bonfiglio, M. Cianciosa, et al., NF 57, 076014 (2013)
4 R. Fitzpatrick, NF 33, 1049 (1993)
5 S. Cappello, M. Viterbo, 26th EPS Conference, Maastricht (1999)
6 K. Kusano, T. Tamano, T. Sato, NF 31, 1923 (1991)
7 F. Ebrahimi, V.V. Mirnov, S.C. Prager et al., PoP 15, 055701 (2008)
8 S. Spagnolo, M. Zuin et al., NF 51 083038 (2011)
