Analysis of eta_imode by reactive and dissipative descriptions and the effects of magnetic q and negative shear on the transport

Abstract

Ion temperature gradient driven modes are studied in the short wavelength region by using a three pole reactive fluid model and an adiabatic E X B convection model, as well as the gyro-Landau fluid model. In all of the above models the parallel ion dynamics is included and the results have been compared both analytically and numerically. Furthermore, the effects of the magnetic safety factor q on the growth rate and transport coefficient xi have been investigated. The maximum of xi as a function of the mode number is computed, and the stabilizing effect of the negative magnetic shear has been studied.

Effects of parallel ion motion on electromagnetic toroidal ion temperature gradient modes in a fluid model

“…The trend is seen in Ref. 11, although finite b effects are absent there. With our choice of parameters (similar to the Cyclone DIII-D case 36 ), the acoustic mode (not being sensitive to g i ) weakens the pure g i mode.…”

“…The ion Landau resonance is taken into account in our model by adapting the Landau part of a gyro-Landau fluid model. 11,[26][27][28] It is shown that this complement (glf) may enhance the g i stabilization but otherwise that it gives growth, frequency, and ballooning properties which are similar to the case without ion Landau resonance being taken into account. The stabilization of the pure ITG mode with decreasing…”

“…[1][2][3][4][5][6][7][8][9] Although a kinetic description of the plasma is more detailed than a fluid description, the latter may give simpler and more explicit results. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] Also the access of computing power is in general not crucial with fluid codes. They normally may be run for times longer than the transport time scale contrary to kinetic codes.…”

“…1,2,4,5 The model is basically reactive (i.e., collisionless) and has been successfully used to study effects such as electron trapping and impurities on mode structure and particle and energy transport and confinement. [11][12][13][18][19][20][21][22][23][24][25] In the original version of the model, the phase velocity of the drift modes along the background magnetic field is assumed to be much larger than the ion thermal velocity.…”

Analytical eigenvalue solution for ηi modes of general modewidth

“…10,11 After extensive rearranging of terms we obtain 1. This term is in better agreement with kinetic theory in an expansion in FLR and magnetic drift 11 but complicates the eigenvalue equation considerably.…”