LETTER TO THE EDITOR Modelling the influence of temperature anisotropies on poloidal asymmetries of density in the core of rotating plasmas

A consistent set of equations is derived to model poloidal density asymmetries induced by temperature anisotropies in tokamak rotating plasmas. The model can be applied to compute poloidal density asymmetry of highly-charged impurities due to additional plasma heating. PACS numbers: 52.25.Dg,52.25.Vy,52.35.Hr,52.50.Gj,52.50.Qt,52.55.Fa,52.65.Ff Submitted to: This is a preprint of a paper published in Nuclear Fusion (2014) vol 24,072003. The final version is available at http://iopscience.iop.org/0029-5515/54/7/072003/ Letter to the Editor 2 In tokamaks, additional heating can affect the poloidal asymmetry of impurity densities, as recently measured in the core of Alcator C-Mod plasmas [1], and already proposed in [2]. The possibility of influencing the poloidal potential by heating with waves in the ion-cyclotron (ICRF) and in the electron-cyclotron range of frequencies was already investigated in [3] (and therein citations), and a simplified model of the ICRF effects has been recently suggested in [4]. Since plasmas generally rotate at toroidal speeds large enough to affect the density of heavy ion, it is necessary to simultaneously account for plasma rotation and for temperature anisotropies in the calculation of poloidal density asymmetries of highly charged impurities. Since the time scale of parallel equilibration is smaller than the characteristic time of cross-field transport for impurities, it is justified to analyze the parallel dynamics separately on each flux surface, by taking the limit of negligible Larmor radius and neglecting the drift terms which are connected with the calculation of the neoclassical transport, which is not the purpose of this work. Precisely, we consider here the zeroth-order equation of the usual expansion in the small parameter δ = ρi/L⊥ of the neoclassical transport theory [5], where ρi is the (poloidal) Larmor radius and L⊥ is the characteristic macroscopic gradient length, in the presence of a plasma flow V0 comparable to thermal ion velocity vthi = √ 2Ti/mi [6]. However, besides the collision operator, we also take into account the effect of additional operators which describe the impact of auxiliary heating systems. Finally, we consider here only axisymmetric geometry. Closely following the derivation in [6] and working in the velocity coordinate system shifted by the flow velocity V0, the zeroth-order Fokker-Planck (FP) equation for the equilibrium distribution function f0 is ∂f0 ∂t0 + (