TY - JOUR
T1 - How pattern is selected in drift wave turbulence
T2 - Role of parallel flow shear
AU - Kosuga, Y.
N1 - Funding Information:
The author also acknowledge the hospitality of National Institute for Fusion Science, where a part of the work has been conducted. This work was partly supported by the Grants-in-Aid for Scientific Research of JSPS of Japan (JP15K17799, JP15H02155 and JP17H06089), the joint research project in RIAM, and Asada Science Foundation.
Publisher Copyright:
© 2017 Author(s).
PY - 2017/12/1
Y1 - 2017/12/1
N2 - The role of parallel shear flow in the pattern selection problem in drift wave turbulence is discussed. Patterns of interest here are E × B convective cells, which include poloidally symmetric zonal flows and radially elongated streamers. The competition between zonal flow formation and streamer formation is analyzed in the context of modulational instability analysis, with the parallel flow shear as a parameter. For drift wave turbulence with k∥ρs ≲ O(1) and without parallel flow coupling, zonal flows are preferred structures. While increasing the magnitude of parallel flow shear, streamer growth overcomes zonal flow growth. This is because the self-focusing effect of the modulational instability becomes more effective for streamers through density and parallel velocity modulation. As a consequence, the bursty release of free energy may result as the parallel flow shear increases.
AB - The role of parallel shear flow in the pattern selection problem in drift wave turbulence is discussed. Patterns of interest here are E × B convective cells, which include poloidally symmetric zonal flows and radially elongated streamers. The competition between zonal flow formation and streamer formation is analyzed in the context of modulational instability analysis, with the parallel flow shear as a parameter. For drift wave turbulence with k∥ρs ≲ O(1) and without parallel flow coupling, zonal flows are preferred structures. While increasing the magnitude of parallel flow shear, streamer growth overcomes zonal flow growth. This is because the self-focusing effect of the modulational instability becomes more effective for streamers through density and parallel velocity modulation. As a consequence, the bursty release of free energy may result as the parallel flow shear increases.
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U2 - 10.1063/1.5001857
DO - 10.1063/1.5001857
M3 - Article
AN - SCOPUS:85038435762
SN - 1070-664X
VL - 24
JO - Physics of Plasmas
JF - Physics of Plasmas
IS - 12
M1 - 122305
ER -