Negative viscosity from negative compressibility and axial flow shear stiffness in a straight magnetic field

Journal Article · Thu Mar 23 00:00:00 EDT 2017 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4978956· OSTI ID:1346872

Li, J. C. ; Diamond, P. H.

Here, negative compressibility ITG turbulence in a linear plasma device (CSDX) can induce a negative viscosity increment. However, even with this negative increment, we show that the total axial viscosity remains positive definite, i.e. no intrinsic axial flow can be generated by pure ITG turbulence in a straight magnetic field. This differs from the case of electron drift wave (EDW) turbulence, where the total viscosity can turn negative, at least transiently. When the flow gradient is steepened by any drive mechanism, so that the parallel shear flow instability (PSFI) exceeds the ITG drive, the flow profile saturates at a level close to the value above which PSFI becomes dominant. This saturated flow gradient exceeds the PSFI linear threshold, and grows with $$\nabla T_{i0}$$ as $$|\nabla V_\parallel| / |k_\parallel c_s| \sim|\nabla T_{i0}|^{2/3} / (k_\parallel T_{i0})^{2/3}$$. This scaling trend characterizes the effective stiffness of the parallel flow gradient.

• Research Organization: Univ. of California, San Diego, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Fusion Energy Sciences (FES)
• Grant/Contract Number: FG02-04ER54738
• OSTI ID: 1346872
• Alternate ID(s): OSTI ID: 1348956
• Journal Information: Physics of Plasmas, Vol. 24, Issue 3; ISSN 1070-664X
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY