Modification on the gyrokinetic quasi-neutrality condition due to large flow

Miyato, Naoaki; Scott, B. D.*

Reduced kinetic models such as gyrokinetic models are constructed by phase space transformation from particle phase space to guiding-centre phase space. In the reduced quasi-neutrality condition or the Poisson equation for electrostatic potential, particle density should be represented in terms of guiding-centre things. It is called push-forward representation of particle density. Recently a reduced kinetic model with large flow was derived by modifying the standard guiding-centre transformation. The model can be regarded as a natural extension of the standard model to the large flow regime because the symplectic part in the guiding-centre phase space Lagrangian is the same as the standard one formally. The push-forward representation of particle density or the reduced quasi-neutrality condition in the transonic case is derived by the variational method. It is found that corrections due to the flow appear in the polarisation density.