关键词: 测地声模, 低-高模转换, 蝌蚪定域化, Langer变换

Abstract:

Based on the Braginskii’s cold ion fluid model，using the quasi-toroidal coordinate system, the two partial differential equations of perturbed density and electrostatic potential describing axial-symmetric (zero toroidal mode number) sound waves have been derived. The coupled equations are then solved for the geodesic acoustic mode (GAM) by making use of the WKB method and Langer transform to obtain the uniformly valid radial mode structure over WKB turning point, and the eigen-frequencies are determined. It is found that no continuum solution for GAM is possible. The near-zero mode frequencies are identified to be associated with the “high energy” excited states in a sense of Schrödinger equation. It is also argued that the radial structure consistency with GAM ordering demands the “tadpole” localization. The implication of the “tadpole” localization to “multi-GAM co-existence” observed is experimentally discussed.

Key words: Geodesic acoustic mode, L-H transition, Tadpole localization, Langer transform