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Low-frequency instabilities locally enhanced by parallel flow velocity shears in magnetized plasmas

Published online by Cambridge University Press:  20 December 2006

T. KANEKO ,
H. SAITO ,
S. ISHIGURO  and
R. HATAKEYAMA
T. KANEKO
Affiliation:
Department of Electronic Engineering, Tohoku University, Sendai 980-8579, Japan
H. SAITO
Affiliation:
Department of Electronic Engineering, Tohoku University, Sendai 980-8579, Japan
S. ISHIGURO
Affiliation:
National Institute for Fusion Science, Oroshi-cho 322-6, Toki 509-5292, Japan
R. HATAKEYAMA
Affiliation:
Department of Electronic Engineering, Tohoku University, Sendai 980-8579, Japan
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Abstract

Three-dimensional electrostatic particle simulations are performed in order to investigate the effects of ion flow parallel to magnetic-field lines and their velocity shears on low-frequency plasma instabilities in detail. In the case where the ion drift speed is so small that the low-frequency instabilities cannot take place, the ion-acoustic wave is destabilized by introducing the ion-flow velocity shear. The ion-acoustic wave is locally destabilized in the large velocity shear region. On the other hand, the ion-cyclotron instability is also destabilized when the ion drift speed exceeds a certain threshold. The flow velocity shear enhances not only the fundamental mode but also the high harmonic modes. As a result, the spiky fluctuations in the time domain are locally observed in the velocity shear region, which are caused by the simultaneous existence of several coherent ion-cyclotron harmonics.

Type
Papers
Information
Journal of Plasma Physics , Volume 72 , Issue 6 , December 2006 , pp. 989 - 992
Copyright
2006 Cambridge University Press

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