Analysis of the validity of the asymptotic techniques in the lower hybrid wave equation solution for reactor applications

Journal Article · Thu Nov 15 04:00:00 EST 2007 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2805435· OSTI ID:21069897

Cardinali, A; Morini, L; Castaldo, C; Cesario, R; Zonca, F ^[1]

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1. Associazione Euratom-ENEA sulla Fusione, C.P. 65-I-00044-Frascati, Rome (Italy)

Knowing that the lower hybrid (LH) wave propagation in tokamak plasmas can be correctly described with a full wave approach only, based on fully numerical techniques or on semianalytical approaches, in this paper, the LH wave equation is asymptotically solved via the Wentzel-Kramers-Brillouin (WKB) method for the first two orders of the expansion parameter, obtaining governing equations for the phase at the lowest and for the amplitude at the next order. The nonlinear partial differential equation (PDE) for the phase is solved in a pseudotoroidal geometry (circular and concentric magnetic surfaces) by the method of characteristics. The associated system of ordinary differential equations for the position and the wavenumber is obtained and analytically solved by choosing an appropriate expansion parameter. The quasilinear PDE for the WKB amplitude is also solved analytically, allowing us to reconstruct the wave electric field inside the plasma. The solution is also obtained numerically and compared with the analytical solution. A discussion of the validity limits of the WKB method is also given on the basis of the obtained results.

• OSTI ID: 21069897
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 11 Vol. 14; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
AMPLITUDES
ANALYTICAL SOLUTION
ASYMPTOTIC SOLUTIONS
ELECTRIC FIELDS
LOWER HYBRID CURRENT DRIVE
LOWER HYBRID HEATING
MAGNETIC SURFACES
NONLINEAR PROBLEMS
PLASMA
PLASMA CONFINEMENT
PLASMA EXPANSION
TOKAMAK DEVICES
WAVE EQUATIONS
WAVE PROPAGATION
WKB APPROXIMATION