Speaker
Francesco Palermo
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P1.1100.pdf
Complex-eikonal methods applied to geodesic acoustic modes
F. Palermo1 , E. Poli1 , A. Bottino1 , A. Ghizzo2
1 Max-Planck-Institut für Plasmaphysik, 85748 Garching, Germany
2 Institut Jean Lamour, University of Lorraine, F-54506 Vandoeuvre les Nancy, France
The tokamak represents a very complex system in which several actors such as drift waves,
streamers, turbulence, zonal flow, geodesic acoustic modes (GAMs)... interact each other
defining the transport properties of the plasma.
GAMs represent the oscillation counterpart of
the zonal flow and have received much attention
for their potential role in the energy confinement
in plasma fusion domain. In particular they inter-
act with turbulence in an inhomogeneous envi-
ronment in which plasma shape and profile gra-
dients strongly affects their amplitude and their
position [1, 2]. Because of the complexity of
the system, it is crucial to develop and to apply
Figure 1: Electric field evolution of GAM in (time,
methods that allow to have simple and accurate radial) plane. Overlapped it is shown the ray paths
descriptions of specific properties of plasma be- predicted by using the geometrical optics methods.
havior. In this way, it is possible to distinguish
in an intuitive and useful manner relevant aspects of global physical systems. To this purpose,
ray method or geometrical optics provides a very powerful tool that has been applied in many
important problems related to wave propagation and energy transport. By using the paraxial
WKB (pWKB) method [3, 4] and a complex-eikonal approach [5], we describe several GAM
properties such as amplitude, shape evolution and energy flux of GAM in homogeneous and in-
homogeneous equilibria. These findings allow us to predict the GAM evolution, in simulations
(see Fig. 1) performed with the particle-in-cell code ORB5 [6, 7].
References
[1] F. Palermo et al., Physics of Plasmas 24, 072503, (2017)
[2] F. Palermo et al., 44rd EPS Conference on Plasma Physics P4.160, (2017)
[3] G. V. Pereverzev, Physics of Plasmas 5, 3529, (1999)
[4] E. Poli et al., Physics of Plasmas 6, 5, (1999)
[5] E. Mazzuccato, Physics of Plasmas 1, 1855 (1989)
[6] S. Jolliet et al., Comput. Phys. Commun. 177, 409 (2007)
[7] A. Bottino and E. Sonnendrucker, J. Plasma Phys. 81, 435810501 (2015)
