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arXiv · 1510.06105

Fast excitation of geodesic acoustic mode by energetic particle beams

Jintao Cao·Zhiyong Qiu·Fulvio Zonca
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Abstract

A new mechanism for Geodesic acoustic mode (GAM) excitation by a not fully slowed down energetic particle (EP) beam is analysed to explain experimental observations in Large Helical Device. It is shown that the positive velocity space gradient near the lower-energy end of the EP distribution function can strongly drive GAM unstable. The new features of this EP-induced GAM (EGAM) are: 1. no instability threshold in the pitch angle; 2. the EGAM frequency can be higher than the local GAM frequency; and 3. the instability growth rate is much larger than that driven by a fully slowed down EP beam.

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Jintao Cao, Zhiyong Qiu, Fulvio Zonca. 2015-10-21. Fast excitation of geodesic acoustic mode by energetic particle beams. https://doi.org/10.1063/1.4938277

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