Abstract Details
Abstracts
Author: Alan D Turnbull
Requested Type: Poster
Submitted: 2019-02-22 20:26:51
Co-authors: G. Kramer, E.M. Bass, B. Tobias
Contact Info:
General Atomics Inc.
PO Box 85608
San Diego, CA 92186
USA
Abstract Text:
Fast particle-driven Alfven eigenmodes have been observed to exhibit a radially varying phase shift in steady state that is inconsistent with the predictions of linear ideal MHD. While several candidate non-ideal effects have been shown to yield non-zero phase shifts [1,2], the real origin is not clear: different non-ideal effects produce radically different phase shifts in either direction. Recently, however, it has been found that the phase shift is directly related to an additional Poynting flux that arises and corresponds to energy transport between the drive location and damping locations in the steady-state driven case [3]. In the present case, the Poynting flux is associated with local adjustments in the mode phase. The basic assumption is that the main modification to the linear mode structure in the non-ideal nonlinear steady state situation is just the establishment of local phase shifts. These are such that they are consistent with the overall power flow through the system, with divergence consistent with the kinetic sources and sinks as well as the changing mode amplitude in the case of a growing or damped mode. In general, the situation is analogous to the classic situation described by Poynting in 1883 of a battery and resistor or capacitor connected by a wire, where the energy transfer from the battery to the resistor/capacitor occurs through the surrounding fields, not through electron motion in the wire. In either case, the Poynting flux provides a different perspective on the system, allowing one to bypass the actual detailed non-ideal mechanisms that provide non-ideal drive and damping to determine the wave front curvature (i.e. the radial phase shift variation) simply from the location of the drive or damping.
Work supported by US DOE under DE-FC02-04ER54698 and DE-FG02-95ER54309
[1] D.A. Spong, E.M. Bass, W. Deng, W.W. Heidbrink, Z. Lin, B. Tobias, M.A. Van Zeeland, M.E. Austin, C.W. Domier, a
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