The helicity of flow field is an important quantity for describing the topological feature of turbulent fluids and plasmas. In this work, we discuss how helicity is determined in turbulent plasmas, by considering the drift wave turbulence and the parallel velocity gradient driven turbulence as concrete examples. Helicity evolution for each turbulence is derived and compared against the simulation data. Links between the plasma helicity and the transport channels, such as particle transport and momentum transport, are demonstrated. Several applications including the excitation of the 3D flow patterns in fusion plasmas and dynamo action in astrophysical plasmas are discussed.
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